Abstract
Background
Long-acting bronchodilators comprising long-acting beta2-agonists and the anticholinergic agent tiotropium are commonly used, either on their own or in combination, for managing persistent symptoms of chronic obstructive pulmonary disease. Patients with severe chronic obstructive pulmonary disease who are symptomatic and who suffer repeated exacerbations are recommended to add inhaled corticosteroids to their bronchodilator treatment. However, the benefits and risks of adding inhaled corticosteroid to tiotropium and long-acting beta2-agonists for the treatment of chronic obstructive pulmonary disease are unclear.
Objectives
To assess the relative effects of adding inhaled corticosteroids to tiotropium and long-acting beta2-agonists treatment in patients with chronic obstructive pulmonary disease.
Search methods
We searched the Cochrane Airways Group Specialised Register of trials (February 2011) and reference lists of articles.
Selection criteria
We included parallel group, randomised controlled trials of three months or longer comparing inhaled corticosteroid and long-acting beta2-agonist combination therapy in addition to inhaled tiotropium against tiotropium and long-acting beta2-agonist treatment for patients with chronic obstructive pulmonary disease (COPD).
Data collection and analysis
Two review authors independently assessed trials for inclusion and then extracted data on trial quality and the outcome results. We contacted study authors for additional information. We collected information on adverse effects from the trials.
Main results
One trial (293 patients) was identified comparing tiotropium in addition to inhaled corticosteroid and long-acting beta2-agonist combination therapy to tiotropium plus long-acting beta2-agonist. The study was of good methodological quality, however it suffered from high and uneven withdrawal rates between the treatment arms. There is currently insufficient evidence to know how much difference the addition of inhaled corticosteroids makes to people who are taking tiotropium and a long-acting beta2-agonist for COPD.
Authors’ conclusions
The relative efficacy and safety of adding inhaled corticosteroid to tiotropium and a long-acting beta2-agonist for chronic obstructive pulmonary disease patients remains uncertain and additional trials are required to answer this question.
Medical Subject Headings (MeSH): Administration, Inhalation; Adrenal Cortex Hormones [*administration & dosage]; Adrenergic beta-Agonists [*administration & dosage]; Delayed-Action Preparations [administration & dosage]; Drug Therapy, Combination [methods]; Pulmonary Disease, Chronic Obstructive [*drug therapy]; Randomized Controlled Trials as Topic; Scopolamine Derivatives [*administration & dosage]
MeSH check words: Humans
BACKGROUND
Description of the condition
Chronic obstructive pulmonary disease (COPD) is a respiratory disease characterised by chronic and progressive breathlessness, cough, sputum production, and airflow obstruction, which leads to restricted activity and poor quality of life (GOLD). COPD comprises a combination of bronchitis and emphysema and involves chronic inflammation and structural changes in the lung. Cigarette smoking is the most important risk factor, however air pollution and occupational dust and chemicals are also recognised risk factors. The World Health Organization (WHO) has estimated that COPD is the fourth or fifth most common single cause of death worldwide and the treatment and management costs present a significant burden to public health. Furthermore, because of the slow onset and the under-recognition of the disease, it is heavily under-diagnosed (GOLD). COPD is a progressive disease leading to decreased lung function over time, even with the best available care. There is currently no cure for COPD though it is both a preventable and treatable disease. As yet, apart from smoking cessation and non-pharmacological treatments such as long-term oxygen therapy in hypoxic patients, no intervention has been shown to reduce mortality (GOLD). Management of the disease is multifaceted and includes reducing risk factors (van der Meer 2001), pharmacological treatments (GOLD; NICE 2010), education (Effing 2007) and pulmonary rehabilitation (Lacasse 2006). Pharmacological therapy is aimed at relieving symptoms, improving exercise tolerance and quality of life, improving lungfunction, or preventing and treating exacerbations. COPD exacerbations impair patients’ quality of life (GOLD). Furthermore, a large part of the economic burden of COPD is attributed to the cost of managing exacerbations, particularly those resulting in use of acute care services or hospitalisations (Hutchinson 2010). Appropriate pharmacological management of the disease is therefore important to reduce and prevent exacerbations.
Description of interventions
COPD pharmacological management tends to begin with one treatment and additional therapies are introduced, as necessary, to control symptoms (GOLD). The first step is often a short-acting bronchodilator for control of breathlessness, when needed: either a short-acting beta2-agonist (SABA) or the short-acting anticholinergic ipratropium. For persistent or worsening breathlessness associated with lung function decline long-acting bronchodilators may be introduced (GOLD). Long-acting bronchodilators include long-acting beta2-agonists (LABA), such as salmeterol or formoterol, and the long-acting anticholinergic agent tiotropium. Regular treatment with long-acting bronchodilators may be more efficient and convenient than treatment with regular short-acting bronchodilators (Beeh 2010). However, the Global Initiative for Chronic Obstructive Pulmonary Disease (GOLD) guidelines do not specify a preference between the two drug classes. For symptomatic patients with severe or very severe COPD (FEV1 < 50% predicted) and with repeated exacerbations GOLD recommends the addition of inhaled corticosteroids (ICS) to bronchodilator treatment. The potential risks or benefits of treatment with a LABA and ICS combination inhaler compared to tiotropium are uncertain (Welsh 2010), as are the risks or benefits of treatment with a combination inhaler in addition to tiotropium, which will be explored in this review.
How the intervention might work
Tiotropium
Tiotropium is an anticholinergic agent, blocking the action of the neurotransmitter acetylcholine. It has an antagonistic effect on muscarinic acetylcholine receptors. Tiotropium has similar affinity for the five different subtypes of muscarinic receptors (M1 to M5), however airway smooth muscle expresses only the M2 and M3 subtypes (Proskocil 2005). Activation of the M3 receptor stimulates a number of intracellular signalling cascades leading to changes in intracellular Ca2+ homeostasis and contraction of smooth muscle. Tiotropium dissociates slowly from M3 receptors giving a bronchodilator effect lasting over 24 hours, but it dissociates rapidly from M2 receptors, which appear to be feedback inhibitory receptors (Barr 2005).
Tiotropium has gained widespread acceptance for its effects on symptoms and exacerbations as a once daily maintenance therapy in stable COPD (Barr 2005; GOLD). In an earlier Cochrane review (Barr 2005), tiotropium was shown to reduce the primary endpoint of COPD exacerbations compared to placebo (OR 0.75; 95% CI 0.66 to 0.85). Within the same review, tiotropium was also associated with a significant benefit over placebo measuring breathlessness, quality of life and a reduction in exacerbations requiring hospitalisation. Similar effects on symptoms and exacerbations were confirmed in a more recent, large randomised control trial of almost 6000 patients followed for over four years (Tashkin 2008). There was, however, no significant effect of tiotropium on lung function decline in this longer study. Anticholinergic side effects that may occur with tiotropium include dry mouth, constipation and tachycardia (Tashkin 2008).
Inhaled corticosteroids (ICS) and long-acting beta2-agonist (LABA)
Inhaled beta2-agonists activate beta2-receptors in the smooth muscle of the airway leading to a cascade of reactions that results in bronchodilation. Beta2-agonists may also act through other mechanisms, such as respiratory muscle function or mucociliary clearance, because patients have shown improvement in symptoms whilst showing no improvement in lung function tests. Beta2- agonists are particularly useful bronchodilators because they reverse bronchoconstriction regardless of the initial cause. The commonly used long-acting beta2-agonists, salmeterol and formoterol, both have a higher selectivity for beta2-receptors than beta1-receptors. Beta2-receptors are the predominant adrenergic receptors in bronchial smooth muscle and beta1-receptors are the predominant receptors in the heart, although 10% to 50% of the total beta-receptors in the heart are comprised of beta2-receptors (Wallukat 2002). The presence of beta2-receptors in the heart raises the possibility that even highly selective beta2-agonists may have cardiac effects. The mechanism for activating beta2-receptors differs between formoterol and salmeterol. Formoterol is taken up into a membrane depot from where it gradually leaks out to interact with the receptor, whilst salmeterol binds near the receptor allowing it to remain at the receptor site continually binding and releasing (Johnson 1998). In both cases stimulation of the beta2-receptors leads to changes in intracellular Ca2+ homeostasis and bronchodilation (Tanaka 2005). The duration of action for long-acting beta2-agonists is approximately 12 hours, and LABAs are usually taken twice daily.
As with tiotropium, LABAs are used as ’symptom controllers’ in stable COPD. A prior Cochrane review found that LABAs improve lung function compared to placebo (Appleton 2006). A more recent, large (3045 patients) long-term (three year) randomised controlled trial compared salmeterol to placebo (TORCH) (Calverley 2007). Salmeterol use was associated with an increase in lung function and a significant reduction in moderate or severe exacerbations compared with placebo (OR 0.85, P < 0.001). A systematic review which included the TORCH study and another 13 trials, with a total of 6453 participants, showed that treatment with a LABA reduced the rate of exacerbations and improved lung function and quality of life compared to placebo but had no effect on mortality (Rodrigo 2008). Possible side effects of LABAs include cardiac effects such as arrhythmia and palpitations, muscle tremors, head ache and dry mouth (Berger 2008). Inhaled corticosteroids are anti-inflammatory drugs. They reduce the rate of exacerbations and the rate of decline in quality of life compared to placebo without any effect on overall mortality or the long-term decline in FEV1 (Agarwal 2010; GOLD; Yang 2007). Inhaled corticosteroids are licensed as combination inhalers with long-acting beta2-agonists. The most common combinations of inhaled corticosteroid and long-acting beta2-agonist in combination inhalers are fluticasone and salmeterol and budesonide and formoterol. Combination inhalers reduce exacerbation rates and all-cause mortality, and improve lung function and quality of life compared to placebo (Nannini 2007). These effects are thought to be greater for combination inhalers than with the component preparations (GOLD). However, inhaled corticosteroids, alone or in combination with beta2-agonists, may increase the risk of pneumonia (GOLD; Singh 2010).
Why it is important to do this review
Patients with severe COPD who are symptomatic and have repeated exacerbations are recommended to add inhaled corticosteroids (ICS) to their bronchodilator treatment (LABA, anticholinergic, or both), most commonly using LABA and ICS combination inhalers. It is unclear what potential clinical advantages arise by combining tiotropium with LABA and ICS compared to tiotropium plus LABA only for these patients. It has been suggested that adding combination inhaler therapy to tiotropium treatment may be beneficial for exacerbations and hospitalisations, which are important sources of healthcare resource utilisation and the cost in COPD (Najafzadeh 2008). This review is necessary to specify and quantify the potential benefits from the combination treatment with LABA, ICS and tiotropium compared to LABA and tiotropium.
This review will form part of a suite of reviews on the various combinations of tiotropium, long-acting beta2-agonists and inhaled corticosteroids for the treatment of COPD. These reviews will ultimately be summarised in an overview. The first of these reviews compared a combination of inhaled corticosteroids and long-acting beta2-agonist with tiotropium (Welsh 2010) and further reviews are in preparation comparing alternate permutations of these three drugs.
OBJECTIVES
To compare the relative effects on measures of quality of life, exacerbations, lung function and serious adverse events in patients with chronic obstructive pulmonary disease randomised to the following therapies:
inhaled tiotropium, long-acting beta2-agonist and corticosteroid versus inhaled tiotropium and long-acting beta2-agonist.
METHODS
Criteria for considering studies for this review
Types of studies
We included only randomised controlled trials with a parallel group design of at least 12 weeks duration. We did not exclude studies on the basis of blinding.
Types of participants
We included populations with a diagnosis of chronic obstructive pulmonary disease. We only included studies where an external set of criteria had been used to screen participants for this condition (for example Global Initiative for Obstructive Lung Disease (GOLD), American Thoracic Society (ATS), British Thoracic Society (BTS), The Thoracic Society of Australia and New Zealand (TSANZ)).
Types of interventions
Inhaled corticosteroid and long-acting beta2-agonist (in either a single combination inhaler or two separate inhalers) and tiotropium bromide compared to inhaled long-acting beta2-agonists and tiotropium administered by any inhalation device.
Types of outcome measures
Primary outcomes
Quality of life (measured with a validated scale for COPD, e.g. St George’s Respiratory Questionnaire, Chronic Respiratory Disease Questionnaire)
Exacerbations, requiring short burst oral corticosteroids or antibiotic, or both
Pneumonia
Mortality, all-cause
Secondary outcomes
Hospital admissions, all causes and due to exacerbations
Disease specific mortality, if independently adjudicated
Forced expiratory volume in one second (FEV1)
Serious adverse events, all-cause, non-fatal
Withdrawals
Search methods for identification of studies
Electronic searches
We identified trials using the Cochrane Airways Group Specialised Register of trials, which is derived from systematic searches of bibliographic databases including the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library), MED-LINE, EMBASE, CINAHL, AMED, and PsycINFO; and hand-searching of respiratory journals and meeting abstracts (please see the Airways Group search methods for further details). The search was not limited by language. All records in the Specialised Register coded as ’COPD’ were searched using the following terms: (tiotropium or spiriva)
AND
(((budesonide or fluticasone or beclomethasone or mometasone or ciclesonide or steroid* or corticosteroid*) and (*formoterol or salmeterol or indacaterol or (beta* and agonist*))) or (symbicort or viani or seretide or advair or foster or fostair or inuvair or fostex or kantos or combination*))
We also conducted a search of clinicaltrials.gov. The search was carried out in February 2011.
Searching other resources
We reviewed the reference lists of the primary study and review articles for references to other trials. We contacted authors of identified trials and manufacturers to ask them to identify other published or unpublished studies.
Data collection and analysis
Selection of studies
Both of us screened the titles and abstracts of citations retrieved through literature searches and obtained those deemed to be potentially relevant. We assigned each reference to a study identifier and assessed them against the inclusion criteria of this protocol.
Data extraction and management
We extracted information from the included study for the following characteristics:
design (design, total duration study and run in, number of study centres and location, withdrawals, date of study);
participants (N, mean age, age range, gender, COPD severity, diagnostic criteria, baseline lung function, smoking history, inclusion criteria, exclusion criteria);
interventions (run-in, intervention treatment and inhaler type, control treatment and inhaler type);
outcomes (primary and secondary outcomes specified and collected, time points reported).
Both of us extracted data from the study into a data collection form. We discussed and resolved any discrepancies in the data, or consulted a third party where necessary. We transferred data from the data collection forms into Review Manager 5.
Assessment of risk of bias in included studies
We assessed the risk of bias according to recommendations outlined in The Cochrane Handbook for Systematic Reviews of Intervetions (Higgins 2011) for the following items:
allocation sequence generation;
concealment of allocation;
blinding of participants and investigators;
incomplete outcome data;
selective outcome reporting.
We graded each potential source of bias as low, high or unclear risk of bias. We also planned to note other sources of bias.
Measures of treatment effect
Dichotomous data
We analysed dichotomous data variables (such as mortality and withdrawals) using Mantel-Haenszel odds ratios using a fixed-effect model with 95% confidence intervals (CI). If events had been rare we would have employed the Peto odds ratio since this does not require a continuity correction for zero cells. If count data had not been available as the number of participants experiencing an event, we would have analysed it as continuous, time-to-event or rate ratios depending on how it had been reported. This included the outcomes: hospital admissions, exacerbations, and serious adverse events. Reported rate ratios would have been transformed into log rate ratios and analysed using a fixed-effect model and the generic inverse variance (GIV) in Review Manager 5.
Continuous data
We analysed continuous outcome data (such as FEV1 and quality of life) as fixed-effect model mean differences (MD) with 95% confidence intervals. If more than one study had been included in the review, we would have analysed continuous outcome data as fixed-effect model mean differences if the same scale had been used, and standardised mean differences if different scales had been employed in different studies. If treatment effects had been reported as a mean difference with a CI or an exact P value, we would have calculated the standard error and entered it with the mean difference and combined the results using a fixed-effect GIV model in Review Manager 5. If data had not been available for the same time point in all studies, the closest time points would have been used. The second alternative would have been to use end of study as the time of analysis for all studies.
We planned to use intention-to-treat (ITT) analysis on outcomes, from all randomised participants where possible, for primary analyses.
We planned to calculate the numbers needed to treat from the pooled odds ratio and its confidence interval and to apply it to appropriate levels of baseline risk.
Unit of analysis issues
We analysed dichotomous data using participants as the unit of analysis (rather than events) to avoid counting the same participant more than once. For continuous data the mean difference based on change from baseline was preferred over mean difference based on absolute values.
Dealing with missing data
We contacted the study investigators in order to verify key study characteristics and to obtain missing numerical outcome data where possible. We also planned to consider the impact of the unknown status of participants who withdrew from the trials as part of a sensitivity analysis.
Assessment of heterogeneity
We planned to assess the amount of statistical variation between study results with the I2 statistic.
Assessment of reporting biases
We minimised reporting bias from non-publication of studies or selective outcome reporting by using a broad search strategy, contacting study authors directly and checking references of included studies. If we found sufficient numbers of trials, we planned to visually inspect funnel plots.
Data synthesis
We planned to present the findings of our primary outcomes in a summary of findings table using GradePro software and the recommendations outlined in The Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2011), if there had been more than one eligible study.
Subgroup analysis and investigation of heterogeneity
We planned to subgroup studies according to:
types of long-acting beta-agonist and inhaled corticosteroid;
severity of disease at baseline;
tiotropium formulation.
Sensitivity analysis
We planned to assess the sensitivity of our primary outcomes to degree of bias by comparing the overall results with those exclusively from trials assessed as being at low risk of bias.
RESULTS
Description of studies
Results of the search
An initial search (July 2010) gave 101 references and additional searches gave a further 16 references (February 2011) and nine references (July 2011). Of the total 126 references we identified nine as potentially relevant, which we obtained in full text for further assessment. Five of these citations were eligible for inclusion and they all belonged to the study Aaron 2007 (see Characteristics of included studies).
Included studies
Aaron 2007 was a randomised, double-blind, placebo-controlled trial with a parallel group design. The duration of the study was one year and it was conducted in 27 different medical centres in Canada. There were 293 participants randomised to tiotropium + LABA and ICS (145) and tiotropium + LABA (148). The mean age of the participants was 68 years, the mean FEV1 predicted was 39%, the gender distribution was 58% males and 42% women, and the disease severity of the participants spanned moderate to severe COPD according to the GOLD guideline definitions of COPD. The participants were either given 18 μg of tiotropium (Handihaler) one inhalation daily plus 250 and 25 μg fluticasone and salmeterol (Diskus) two inhalations twice daily or 18 μg oftiotropium (Handihaler) plus 25 μg salmeterol (Diskus) two inhalations twice daily. Participants were instructed to use inhaled albuterol when necessary to relieve symptoms. Respiratory medications such as oxygen, antileukotrienes and methylxanthines, were continued in all patient groups. The primary outcome was the proportion of patients suffering one or more COPD exacerbations. The study was funded by the Canadian Institutes of Health Research and the Ontario Thoracic Society.
Excluded studies
Four studies failed to meet the eligibility criteria for the review (see Characteristics of excluded studies). All four lacked a tiotropium plus LABA treatment group. Three of them were also of crossover design with a treatment period shorter than 12 weeks (Golabi 2006; Hara 2007; Mittmann 2010; Singh 2008).
Risk of bias in included studies
An assessment of the risk of bias is presented in the Characteristics of included studies table.
Allocation
Aaron 2007 reported adequate sequence generation and allocation concealment. Sequence generation was computer-generated and the different inhalers were identical.
Blinding
The blinding in Aaron 2007 was adequate. Both research staff and patients were blinded to the treatment assignment, and clinical data for suspected exacerbations were reviewed by a blinded committee.
Incomplete outcome data
Aaron 2007 suffered from high and uneven withdrawal rates in the different study groups (26% withdrew from the tiotropium + LABA and ICS group and 43% who were on tiotropium + LABA). For most patients, data were recorded throughout the one-year trial period regardless of whether patients discontinued treatment with the study medications. The rate of patients who stopped therapy and did not complete the trial, however, was still relatively large and unevenly distributed between the intervention groups (10% tiotropium + LABA and ICS, and 14% tiotropium + LABA). Mortality data were obtained for all participants with the exception of two participants (1.4%) on tiotropium + LABA and ICS and two (1.4%) on tiotropium + LABA who withdrew and declined further study.
Selective reporting
Aaron 2007 adequately reported outcome data for the primary and secondary outcomes that were pre-specified in the study record.
Effects of interventions
Data and analyses are summarised in Table 1.
Table 1.
Outcome | Effect estimate |
---|---|
Quality of life (SGRQ) | MD −1.02; 95% CI −5.10 to 3.06 |
Number of patients with ≥1 exacerbations | OR 0.81; 95% CI 0.51 to 1.30 |
Number of patients suffering from pneumonia | OR 1.02; 95% CI 0.06 to 16.48 |
Mortality | OR 1.02; 95% CI 0.32 to 3.24 |
Number of patients with ≥1 hospitalisations (all cause) | OR 0.91; 95% CI 0.53 to 1.58 |
Number of patients with ≥1 hospitalisations due to exacerbations | OR 0.63; 95% CI 0.34 to 1.17 |
Pre-dose FEV1 | MD 0.07; 95% CI −0.03 to 0.17 |
Number of patients suffering ≥1 serious adverse events (non-fatal) | OR 1.02; 95% CI 0.20 to 5.14 |
Number of patients suffering ≥1 adverse events | OR 1.58; 95% CI 0.93 to 2.68 |
Total number of patients withdrawn | OR 0.45; 95% CI 0.27 to 0.74 |
Number of patients withdrawn due to adverse events | OR 1.38; 95% CI 0.47 to 4.09 |
Number of patients withdrawn due to lack of efficacy | OR 0.36; 95% CI 0.21 to 0.63 |
Primary outcomes
Aaron 2007 (293 participants) studied changes in health-related quality of life using the St George’s Respiratory Questionnaire (SGRQ). A decrease in SGRQ score indicates an improvement in quality of life and the threshold is four units for a clinically significant difference (SGRQ-C manual 2008). At the end of the study there was substantial uncertainty regarding the difference in effect of tiotropium + LABA and ICS and the tiotropium + LABA treatments on quality of life (MD −1.02; 95% CI −5.10 to 3.06).Aaron 2007 defined COPD exacerbations as a sustained worsening of the patient’s respiratory condition necessitating short-term use of either oral or intravenous steroids, oral or intravenous antibiotics, or both therapies. There was considerable uncertainty and no statistically significant difference in the number of patients who had one or more exacerbations between the tiotropium + LABA and ICS (87/145) and the tiotropium + LABA (96/148) groups (OR 0.81; 95% CI 0.51 to 1.30).
Aaron 2007 reported one case of pneumonia (leading to mechanical ventilation or death) and six deaths (all-cause) in each of the treatment groups. There was considerable uncertainty and no statistically significant differences between the treatment groups (pneumonia: OR 1.02; 95% CI 0.06 to 16.48, and mortality: OR 1.02; 95% CI 0.32 to 3.24).
Secondary outcomes
Data regarding hospitalisations due to exacerbations or any cause were kindly supplied by Aaron 2007 on request. There was no statistically significant difference in the number of patients admitted to hospital due to exacerbation or any cause between the treatment groups (all cause hospitalisation: tiotropium + LABA and ICS 32/145, tiotropium + LABA 35/148, OR 0.91 (95% CI 0.53 to 1.58), and due to exacerbation: tiotropium + LABA and ICS 20/145, tiotropium + LABA 30/148, OR 0.63 (95% CI 0.34 to 1.17)).
Tiotropium + LABA showed no significant difference in pre-bronchodilator FEV1 compared to tiotropium + LABA and ICS (MD 0.07 L; 95% CI −0.03 to 0.17).
There was no statistically significant difference between tiotropium + LABA and ICS (3/145) and tiotropium + LABA (3/148) treatments in the number of patients suffering non-fatal serious adverse events (OR 1.02; 95% CI 0.20 to 5.14). More patients suffered adverse events on tiotropium + LABA and ICS (44/145) than on tiotropium + LABA (32/148) (OR 1.58; 95% CI 0.93 to 2.68), although the difference was not statistically significant.
The number of withdrawals from Aaron 2007 for any reason was high and the withdrawal rate was significantly higher in the tiotropium + LABA group (43%) than in the tiotropium + LABA and ICS group (26%) (OR 0.45; 95% CI 0.27 to 0.74). Aaron 2007 reported the breakdown of the reasons for withdrawing from the study treatment, which included: adverse event, declined further study, lost to follow up, or lack of efficacy. Lack of efficacy was the sum of patients withdrawn from the study treatment because of treatment failure according to physician and patient perceptions of worsening of COPD. The difference between the number withdrawing due to adverse events (OR 1.38; 95% CI 0.47 to 4.09) was not statistically significant, whereas the difference between the number withdrawing due to lack of efficacy was significantly lower in the tiotropium + LABA and ICS group (25/145) than in the tiotropium + LABA group (54/148) (OR 0.36; 95% CI 0.21 to 0.63).
DISCUSSION
This systematic review set out to investigate the long-term (≥three month) effect of tiotropium in combination with LABA and ICS compared to tiotropium + LABA for the treatment of COPD. One randomised, double-blind trial with 293 participants was identified. The Aaron 2007 study was of good methodological quality, however it suffered from high and uneven withdrawal rates between the treatment arms. The data from Aaron 2007 showed considerable uncertainty and no statistically significant difference between patients treated with tiotropium + LABA and ICS, and tiotropium + LABA for the outcomes: health-related quality of life, exacerbations, pneumonia, mortality, hospitalisations, FEV1 and adverse events. The fact that only one, relatively small study was included in this review and that is suffered large and uneven withdrawals makes the results for outcomes with few events or small differences less reliable. However, the statistically significant difference in the number of patients who withdrew due to lack of efficacy may imply some beneficial effect of ICS and LABA + tiotropium compared to LABA + tiotropium treatment. Around 75% of participants in both treatment groups received ICS or ICS and LABA combination therapy before entering the trial (Aaron 2007). If the participants who were on ICS treatment at the time of randomisation represents ICS responders, this could lead to greater drop-outs in the placebo arm when these patients noticed a lack of benefit.
Several systematic reviews have tried to investigate the contribution of ICS to the benefits and risks of combination therapies in COPD. Systematic reviews comparing ICS treatment with placebo and LABA and ICS combination treatment to LABA alone have shown that ICS reduces the occurrence of exacerba tions (Agarwal 2010; Nannini 2007a; Rodrigo 2009) and has positive effects on quality of life and lung function (Nannini 2007a;Rodrigo 2009; Yang 2007). ICS treatment on its own or in combination with LABA has not been shown to have any significant effect on mortality (Nannini 2007a; Rodrigo 2009; Yang 2007). However, pneumonia occurs more frequently with ICS treatment and the elevated risk remained consistent irrespective of whether LABA and ICS combination inhalers were compared to LABA, ICS or to placebo (Nannini 2007a; Rodrigo 2009; Singh 2010). The potential effect of ICS on medical expenses for COPD patients has also been evaluated. Compared to placebo, ICS reduces costs and improves outcomes in patients aged over 50 years, although estimated cost saving per avoided exacerbation is uncertain (Akazawa 2008). The cost effectiveness of LABA and ICS combination therapy compared to LABA monotherapy seems to favour combination therapy based on a significant gain in quality-adjusted life years (Briggs 2010) and potentially an overall savings in total COPD-related exacerbation and therapeutic healthcare costs (Dalal 2010).
In summary, because of the limited evidence presented in this review, It is unclear if adding ICS to tiotropium + LABA will lead to similar clinical improvements, risks and cost effectiveness as when added to LABA monotherapy or placebo.
AUTHORS’ CONCLUSIONS
Implications for practice
There was only a single study conducted with few patients and therefore there are insufficient data to draw any conclusions regarding the long-term effects and risks of tiotropium + LABA and ICS treatment compared to tiotropium + LABA. The relative efficacy and safety of adding ICS to tiotropium + LABA therefore remain uncertain.
Implications for research
Additional large, long-term randomised controlled trials are required to show any potential benefits and risks of taking LABA and ICS combination inhaler together with tiotropium rather than only tiotropium and LABA for COPD patients.
PLAIN LANGUAGE SUMMARY.
The effect of adding inhaled corticosteroids to tiotropium and long-acting beta2-agonists for managing chronic obstructive pulmonary disease
Chronic obstructive pulmonary disease (COPD) is a lung disease which includes the conditions chronic bronchitis and emphysema. COPD is characterised by blockage or narrowing of the airways. The symptoms include breathlessness and a chronic cough. COPD is an irreversible disease that is usually brought on by airway irritants, such as smoking or inhaled dust.
Long-acting beta2-agonists and tiotropium are two types of inhaled medications that help widen the airways (bronchodilators) for up to 12 to 24 hours. These bronchodilators are commonly used to manage persistent symptoms of COPD. They can be used in combination or on their own. Patients with severe COPD who suffer ongoing worsening of symptoms are recommended to add anti-inflammatory inhaled corticosteroids to their bronchodilator treatment. However, the benefits and risks of adding inhaled corticosteroid to tiotropium and long-acting beta2-agonists for the treatment of COPD are unclear.
This review found one study, involving 293 patients, comparing the long-term efficacy and side effects of combining inhaled corticosteroid with tiotropium and a long-acting beta2-agonist. In this study there were not enough patients for us to be able to draw any firm conclusions as to whether combining inhaled corticosteroid with tiotropium and the long-acting beta2-agonist is better or worse than using only tiotropium and the long-acting beta2-agonist. More long-term studies need to be done in order to better understand the effect of treatment with inhaled corticosteroid, tiotropium and a long-acting beta2-agonist.
ACKNOWLEDGEMENTS
We are grateful to Elizabeth Stovold for help designing the search strategy.
CRG Funding Acknowledgement: The National Institute for Health Research (NIHR) is the largest single funder of the Cochrane Airways Group.
Disclaimer: The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the NIHR, NHS or the Department of Health.
SOURCES OF SUPPORT
Internal sources
St George’s University of London, UK.
External sources
NIHR, UK.
Programme grant funding
CHARACTERISTICS OF STUDIES
Characteristics of included studies [ordered by study ID]
Methods | Design: A randomised, double-blind, placebo-controlled, parallel group trial from October 2003 to January 2006. The trial included 27 Canadian medical centres; 20 centres were academic hospital-based pulmonary clinics, 5 were community-based pulmonary clinics, and 2 were community-based primary care clinics | |
Participants |
Population: 293 adults with a clinical history of moderate or severe COPD as defined by ATS and GOLD guidelines Baseline Characteristics: Mean age 68 years. COPD severity moderate to severe with mean FEV1 predicted of 39%. 58% men. Inclusion Criteria: At least 1 exacerbation of COPD that required treatment with systemic steroids or antibiotics within the 12 months before randomisation; age older than 35 years; a history of 10 pack-years or more of cigarette smoking; documented chronic airflow obstruction, with an FEV1/FVC ratio < 0.70 and a post-bronchodilator FEV1 < 65% of the predicted value. Exclusion Criteria: History of physician-diagnosed asthma before 40 years of age; history of physician-diagnosed chronic congestive heart failure with known persistent severe left ventricular dysfunction; those receiving oral prednisone; those with a known hypersensitivity or intolerance to tiotropium, salmeterol, or fluticasone-salmeterol; history of severe glaucoma or severe urinary tract obstruction, previous lung transplantation or lung volume reduction surgery, or diffuse bilateral bronchiectasis; and those WHO were pregnant or were breastfeeding |
|
Interventions |
1. Tiotropium + salmeterol + fluticasone: tiotropium (Spiriva, Handihaler (Boehringer Ingelheim Pharma, Ingelheim, Germany)), 18 g once daily, plus fluticasone-salmeterol (Advair (GlaxoSmithKline)), 250/25 g/puff, 2 puffs twice daily 2. Tiotropium + salmeterol: tiotropium, 18 g once daily, plus salmeterol (Serevent (GlaxoSmithKline, Research Triangle Park, North Carolina)), 25 g/puff, 2 puffs twice daily |
|
Outcomes |
Primary: Proportion of patients with one or more exacerbation of COPD Secondary: Mean number of COPD exacerbations per patient-year; the total number of exacerbations that resulted in urgent visits to a healthcare provider or emergency department; the number of hospitalisations for COPD; the total number of hospitalisations for all causes; changes in health-related quality of life, dyspnoea, lung function |
|
Notes | Co-medication: All study patients were provided with inhaled albuterol and were instructed to use it when necessary to relieve symptoms. Any treatment with inhaled corticosteroids, long-acting beta2-agonists, and anticholinergics that the patient may have been using before entry was discontinued on entry into the study. Therapy with other respiratory medications, such as oxygen, antileukotrienes, and methylxanthines, was continued in all patient groups | |
Risk of bias | ||
Bias | Authors’ judgement | Support for judgement |
Random sequence generation (selection bias) | Low risk | Randomisation was done through central allocation of a randomisation schedule that was prepared from a computer-generated random listing of the 3 treatment allocations, blocked in variable blocks of 9 or 12 and stratified by site |
Allocation concealment (selection bias) | Low risk | The metered-dose inhalers containing placebo, salmeterol, and fluticasone-salmeterol were identical in taste and appearance, and they were enclosed in identical tamper-proof blinding devices. The medication canisters within the blinding devices were stripped of any identifying labelling |
Blinding (performance bias and detection bias) All outcomes |
Low risk | Neither research staff nor patients were aware of the treatment assignment before or after randomisation |
Incomplete outcome data (attrition bias) All outcomes |
Unclear risk | The number of people WHO stopped drug therapy was high, with large variations between the groups (37/145 (26%) tiotropium + LABA/ICS and 64/148 (43%) tiotropium + LABA). However, the number of people who did not complete the trial was lower, although there was still some variations between the groups (15 (10%) tiotropium + LABA/ICS and 20 (14%) tiotropium + LABA). The issue of incomplete data was however addressed by sensitivity analyses of the data for the primary outcome (exacerbations). In the primary analysis it was assumed that all patients who were lost to follow-up did not have an exacerbation (ITT analysis). In the sensitivity analyses it was assumed that patients who were lost to follow-up either all had an exacerbation or had exacerbations at the same rate as those who continued in the study. Both analyses gave a similar result to the primary ITT analysis |
Selective reporting (reporting bias) | Low risk | Results for all listed primary and secondary outcomes were reported |
Characteristics of excluded studies [ordered by study ID]
Study | Reason for exclusion |
---|---|
Golabi 2006 | Four weeks of treatment, only tiotropium alone and salmeterol/fluticasone treatment groups, cross-over design |
Hara 2007 | Eight weeks of treatment, only tiotropium alone and salmeterol/fluticasone treatment groups, cross-over design |
Mittmann 2010 | No tiotropium plus LABA treatment group |
Singh 2008 | Two weeks of treatment, no tiotropium plus LABA treatment group, and of cross-over design |
DATA AND ANALYSES
This review has no analyses.
WHAT’S NEW
Last assessed as up-to-date: 7 February 2011.
Date | Event | Description |
---|---|---|
11 April 2013 | Amended | Funder acknowledgement added |
Footnotes
DECLARATIONS OF INTEREST None known
References to studies included in this review
- Aaron 2007 {published data only} .Aaron SD, Vandemheen K, Ferguson D, FitzGerald M, Maltais F, Boureau J, et al. The Canadian optimal therapy of COPD trial: Design, organization and patient recruitment. Canadian Respiratory Journal. 2004;11(8):581–5. doi: 10.1155/2004/394710. [DOI] [PubMed] [Google Scholar]; Aaron SD, Vandemheen KL, Fergusson D, Maltais F, Bourbeau J, Goldstein R, et al. Tiotropium in combination with placebo, salmeterol, or fluticasone-salmeterol for treatment of chronic obstructive pulmonary disease: a randomized trial. [see comment] [summary for patients in Annals of Internal Medicine 2007 Apr 17;146(8):I12; PMID: 17310044] Annals of Internal Medicine. 2007;146(8):545–55. doi: 10.7326/0003-4819-146-8-200704170-00152. [DOI] [PubMed] [Google Scholar]; Kaplan A. Effects of tiotropium combined with either salmeterol or salmeterol/fluticasone in moderate to severe COPD. Primary Care Respiratory Journal. 2007;16(4):258–60. doi: 10.3132/pcrj.2007.00055. [DOI] [PMC free article] [PubMed] [Google Scholar]; Najafzadeh M, Marra CA, Sadatsafavi M, Aaron SD, Sullivan SD, Vandemheen KL, et al. Cost effectiveness of therapy with combinations of long acting bronchodilators and inhaled steroids for treatment of COPD. Thorax. 2008;63(11):962–7. doi: 10.1136/thx.2007.089557. [DOI] [PubMed] [Google Scholar]; Roisman G. Tiotropium in combination with placebo, salmeterol, or fluticasone-salmeterol for treatment of chronic obstructive pulmonary disease. A randomized trial. Revue de Pneumologie Clinique. 2007;63(6):390–1. doi: 10.7326/0003-4819-146-8-200704170-00152. [DOI] [PubMed] [Google Scholar]
References to studies excluded from this review
- Golabi 2006 {published data only} .Golabi P, Topaloglu N, Karakurt S, Celikel T. Effects of tiotropium and salmeterol/fluticasone combination on lung hyperinflation dyspnea and exercise tolerance in COPD [Abstract] European Respiratory Journal. 2006;Vol. 28(issue Suppl 50):33s. [E304] [Google Scholar]
- Hara 2007 {published data only} .Hara K, Kurashima K, Tokunaga D, Ueno M, Aoyagi K, Isobe Z, et al. Single blind comparison of tiotropium and salmeterol plus fluticasone propionate of treatment in patients with chronic obstructive pulmonary disease (COPD) [Abstract]. American Thoracic Society International Conference; San Francisco, California, USA. May 18-23, 2007; 2007. Poster #A1. [Google Scholar]
- Mittmann 2010 {published data only} .Mittmann N, Hernandez P, Mellström C, Brannman L, Welte T. Cost-effectiveness of budesonide/formoterol added to tiotropium in COPD patients in Canada, Australia and Sweden [Abstract]. European Respiratory Society Annual Congress; Barcelona, Spain. September 18-22. 2010.p. 5183. [Google Scholar]
- Singh 2008 {published data only} .Singh D, Brooks J, Hagan G, Cahn A, O’Connor BJ. Superiority of “triple” therapy with salmeterol/fluticasone propionate and tiotropium bromide versus individual components in moderate to severe COPD. Thorax. 2008;63(7):592–8. doi: 10.1136/thx.2007.087213. [DOI] [PubMed] [Google Scholar]; Singh D, Hagan G, Cahn A, Leonard TB, Riley JH, O’Connor BJ. Individual and combined responses to salmeterol/fluticasone propionate combination (SFC) and tiotropium (Tio) shown in a COPD clinical trial [Abstract]. American Thoracic Society International Conference; Toronto. May 16-21, 2008; 2008. p. A648. [#F10] [Google Scholar]
Additional references
- Agarwal 2010 .Agarwal R, Aggarwal AN, Gupta D, Jindal SK. Inhaled corticosteroids vs placebo for preventing COPD exacerbations. Chest. 2010;137(2):318–25. doi: 10.1378/chest.09-1305. [DOI] [PubMed] [Google Scholar]
- Akazawa 2008 .Akazawa M, Hayflinger DC, Stanford RH, Blanchette CM. Economic assessment of initial maintenance therapy for chronic obstructive pulmonary disease. The American Journal of Managed Care. 2008;14(7):438–48. [PubMed] [Google Scholar]
- Appleton 2006 .Appleton S, Poole P, Smith B, Veale A, Lasserson TJ, Chan MMK, et al. Long-acting beta2-agonists for poorly reversible chronic obstructive pulmonary disease. Cochrane Database of Systematic Reviews. 2006;(Issue 3) doi: 10.1002/14651858.CD001104.pub2. [DOI: 10.1002/14651858.CD001104.pub2] [DOI] [PubMed] [Google Scholar]
- Barr 2005 .Barr RG, Bourbeau J, Camargo Carlos A. Tiotropium for stable chronic obstructive pulmonary disease. Cochrane Database of Systematic Reviews. 2005;(Issue 2) doi: 10.1002/14651858.CD002876.pub2. [DOI: 10.1002/14651858.CD002876.pub2] [DOI] [PMC free article] [PubMed] [Google Scholar]
- Beeh 2010 .Beeh KM, Beier J. The short, the long, and the “ultra-long”: Why duration of bronchodilator action matters in chronic obstructive pulmonary disease. Advances in Therapy. 2010;27(3):150–9. doi: 10.1007/s12325-010-0017-6. [DOI] [PubMed] [Google Scholar]
- Berger 2008 .Berger WE, Nadel JA. Efficacy and safety of formoterol for the treatment of chronic obstructive pulmonary disease. Respiratory Medicine. 2008;102(2):173–88. doi: 10.1016/j.rmed.2007.09.011. [DOI] [PubMed] [Google Scholar]
- Briggs 2010 .Briggs AH, Glick HA, Lozano-Ortega G, Spencer M, Calverley PMA, Jones PW, et al. Is treatment with ICS and LABA cost-effective for COPD? Multinational economic analysis of the TORCH study. European Respiratory Journal. 2010;35(3):532–9. doi: 10.1183/09031936.00153108. [DOI] [PubMed] [Google Scholar]
- Calverley 2007 .Calverley PM, Anderson JA, Celli B, Ferguson GT, Jenkins C, Jones PW, et al. TORCH investigators. Salmeterol and fluticasone propionate and survival in chronic obstructive pulmonary disease. The New England Journal of Medicine. 2007;356(8):775–89. doi: 10.1056/NEJMoa063070. [DOI] [PubMed] [Google Scholar]
- Dalal 2010 .Dalal AA, St Charles M, Petersen HV, Roberts MH, Blanchette CM, Manavi-Zieverink K. Cost-effectiveness of combination fluticasone propionate-salmeterol 250/50 microg versus salmeterol in severe COPD patients. International Journal of Chronic Obstructive Pulmonary Disease. 2010;5:179–87. doi: 10.2147/copd.s10988. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Effing 2007 .Effing T, Monninkhof EEM, van der Valk PPDLPM, Zielhuis GGA, Walters EH, van der Palen JJ, et al. Self-management education for patients with chronic obstructive pulmonary disease. Cochrane Database of Systematic Reviews. 2007;(Issue 4) doi: 10.1002/14651858.CD002990.pub2. [DOI: 10.1002/14651858.CD002990.pub2] [DOI] [PubMed] [Google Scholar]
- GOLD . [Accessed 14th December 2009];Global Initiative for Chronic Obstructive Lung Disease. http://www.goldcopd.com
- Higgins 2011 .Higgins JPT, Green S, editors. Cochrane Handbook for Systematic Reviews of Interventions Version 5.0.2. The Cochrane Collaboration; [updated September 2009]. 2011. Available from www.cochrane-handbook.org. [Google Scholar]
- Hutchinson 2010 .Hutchinson A, Brand C, Irving L, Roberts C, Thompson P, Campbell D. Acute care costs of patients admitted for management of chronic obstructive pulmonary disease exacerbations: contribution of disease severity, infection and chronic heart failure. Internal Medicine Journal. 2010;40(5):364–71. doi: 10.1111/j.1445-5994.2010.02195.x. [DOI] [PubMed] [Google Scholar]
- Johnson 1998 .Johnson M. The beta-adrenoceptor. American Journal of Respiratory and Critical Care Medicine. 1998;158(5 Pt 3):S146–53. doi: 10.1164/ajrccm.158.supplement_2.13tac110. [DOI] [PubMed] [Google Scholar]
- Lacasse 2006 .Lacasse Y, Goldstein R, Lasserson TJ, Martin S. Pulmonary rehabilitation for chronic obstructive pulmonary disease. Cochrane Database of Systematic Reviews. 2006;(Issue 4) doi: 10.1002/14651858.CD003793.pub2. [DOI: 10.1002/14651858.CD003793.pub2] [DOI] [PubMed] [Google Scholar]
- Najafzadeh 2008 .Najafzadeh M, Marra CA, Sadatsafavi M, Aaron SD, Sullivan SD, Vandemheen KL, et al. Cost effectiveness of therapy with combinations of long acting bronchodilators and inhaled steroids for treatment of COPD. Thorax. 2008;63(11):962–7. doi: 10.1136/thx.2007.089557. [DOI] [PubMed] [Google Scholar]
- Nannini 2007 .Nannini L, Cates CJ, Lasserson TJ, Poole P. Combined corticosteroid and long-acting beta-agonist in one inhaler versus placebo for chronic obstructive pulmonary disease. Cochrane Database of Systematic Reviews. 2007;(Issue 4) doi: 10.1002/14651858.CD003794.pub3. [DOI: 10.1002/14651858.CD003794.pub3] [DOI] [PMC free article] [PubMed] [Google Scholar]
- Nannini 2007a .Nannini Luis J, Cates Christopher J, Lasserson Toby J, Poole P. Combined corticosteroid and long-acting beta-agonist in one inhaler versus long-acting beta-agonists for chronic obstructive pulmonary disease. Cochrane Database of Systematic Reviews. 2007;(Issue 4) doi: 10.1002/14651858.CD006829. [DOI: 10.1002/14651858.CD006829] [DOI] [PubMed] [Google Scholar]
- NICE 2010 .National Clinical Guideline Centre . Chronic obstructive pulmonary disease: management of chronic obstructive pulmonary disease in adults in primary and secondary care. National Clinical Guideline Centre; London: 2010. Chronic obstructive pulmonary disease: Management of chronic obstructive pulmonary disease in adults in primary and secondary care. URL: http://guidance.nice.org.uk/CG101/Guidance/pdf/English. [Google Scholar]
- Proskocil 2005 .Proskocil BJ, Fryer AD. Beta2-agonist and anticholinergic drugs in the treatment of lung disease. Proceedings of the American Thoracic Society. 2005;2(4):305–10. doi: 10.1513/pats.200504-038SR. discussion 311-2. [DOI] [PubMed] [Google Scholar]
- Review Manager 5 .The Nordic Cochrane Centre. Cochrane Collaboration . Review Manager (RevMan) Version 5. The Nordic Cochrane Centre; Cochrane Collaboration; Copenhagen: 2008. [Google Scholar]
- Rodrigo 2008 .Rodrigo GJ, Nannini LJ, Rodríguez-Roisin R. Safety of long-acting -agonists in stable COPD: A systematic review. Chest. 2008;133(5):1079–87. doi: 10.1378/chest.07-1167. [DOI] [PubMed] [Google Scholar]
- Rodrigo 2009 .Rodrigo GJ, Castro-Rodriguez JA, Plaza V. Safety and efficacy of combined long-acting beta-agonists and inhaled corticosteroids vs long-acting beta-agonists monotherapy for stable COPD: a systematic review. Chest. 2009;136(4):1029–38. doi: 10.1378/chest.09-0821. [DOI] [PubMed] [Google Scholar]
- SGRQ-C manual 2008 .Jones P. St George’s Respiratory Questionnaire for COPD Patients (SGRQ-C) St George’s, University of London; 2008. [Google Scholar]
- Singh 2010 .Singh S, Loke YK. An overview of the benefits and drawbacks of inhaled corticosteroids in chronic obstructive pulmonary disease. International Journal of Chronic Obstructive Pulmonary Disease. 2010;5:189–95. doi: 10.2147/copd.s6942. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tanaka 2005 .Tanaka Y, Horinouchi T, Koike K. New insights into beta-adrenoceptors in smooth muscle: distribution of receptor subtypes and molecular mechanisms triggering muscle relaxation. Clinical and Experimental Pharmacology and Physiology. 2005;32(7):503–14. doi: 10.1111/j.1440-1681.2005.04222.x. [DOI] [PubMed] [Google Scholar]
- Tashkin 2008 .Tashkin DP, Celli B, Senn S, Burkhart D, Kesten S, Menjoge S, Decramer M. UPLIFT Study Investigators. A 4-year trial of tiotropium in chronic obstructive pulmonary disease. The New England Journal of Medicine. 2008;359(15):1543–54. doi: 10.1056/NEJMoa0805800. [DOI] [PubMed] [Google Scholar]
- van der Meer 2001 .van der Meer RM, Wagena E, Ostelo RWJG, Jacobs AJE, van Schayck O. Smoking cessation for chronic obstructive pulmonary disease. Cochrane Database of Systematic Reviews. 2001;(Issue 1) doi: 10.1002/14651858.CD002999. [DOI: 10.1002/14651858.CD002999] [DOI] [PMC free article] [PubMed] [Google Scholar]
- Wallukat 2002 .Wallukat G. The beta-adrenergic receptors. Herz. 2002;27(7):683–90. doi: 10.1007/s00059-002-2434-z. [DOI] [PubMed] [Google Scholar]
- Welsh 2010 .Welsh EJ, Cates CJ, Poole P. Combination inhaled steroid and long-acting beta2-agonist versus tiotropium for chronic obstructive pulmonary disease. Cochrane Database of Systematic Reviews. 2010;(Issue 5) doi: 10.1002/14651858.CD007891.pub2. [DOI: 10.1002/14651858.CD007891] [DOI] [PubMed] [Google Scholar]
- WHO .World Health Organization Chronic Respiratory Diseases. www.who.int
- Yang 2007 .Yang IA, Fong K, Sim EHA, Black PN, Lasserson TJ. Inhaled corticosteroids for stable chronic obstructive pulmonary disease. Cochrane Database of Systematic Reviews. 2007;(Issue 2) doi: 10.1002/14651858.CD002991.pub2. [DOI: 10.1002/14651858.CD002991.pub2] [DOI] [PubMed] [Google Scholar]
- * Indicates the major publication for the study