Heparin and related substances for treating diabetic foot ulcers

Abstract

This is a protocol for a Cochrane Review (Intervention). The objectives are as follows:

To assess the efficacy and safety of heparin and heparin‐related substances for the treatment of diabetic foot ulcers.

Background

Description of the condition

Data from the World Health Organization (WHO) estimated that in 2011 approximately 366 million people worldwide had diabetes mellitus (DM) (Wild 2004); over 80% of DM is thought to occur in low‐ and middle‐income countries (Bakker 2012a). The International Working Group on the Diabetic Foot (IWGDF) defines a diabetic foot ulcer as a 'full‐thickness' lesion of the skin (Bakker 2012a). It occurs in 16% of people with DM and precedes 85% of foot‐related amputations (Brem 2007). The prevalence of diabetic foot ulcers varies from country to country. In the USA, the lifetime incidence of developing a diabetic foot ulcer may be as high as 25% for the 24 million people with DM, with 1% of this population requiring amputation (Sherman 2010). Every year In Germany 22,000 people with DM lose a leg as a result of diabetic foot ulcers (Simson 2008). South Asians with DM are about 33% more likely to develop a foot ulcer than Europeans (Abbott 2005). The prevalence of diabetic foot ulcers is about 5.6% of those with DM in the Veterans Affairs Hospital of America Seattle, 10.2% in Britain, 10% in India and 14% in China (Li 2010).

Diabetic foot ulcers are caused by multiple pathogenic (disease) mechanisms (Warren 2009). The most frequent etiologies (causes) are peripheral sensory neuropathy (damage to nerves in feet/legs), trauma, deformity, high plantar pressures (pressure on the foot when walking), and peripheral arterial disease (Boyko 1999; Frykberg 2009; Reiber 1999). The etiology of diabetic foot ulcers can be grouped into three major classifications: neuropathic (due to damage of the nerves); ischaemic (due to a poor blood supply); or neuroischaemic (due to damage to the nerves and a poor blood supply). The loss of sensation caused by peripheral neuropathy means that injuries to the feet may not be noticed when they happen, and these, potentially, can develop into more serious wounds. If the blood supply is partially or completely blocked, tissue will begin to die, which can result in the development of painful ulcerations on the feet. For healing to occur it is of crucial importance to have intact microcirculation in the skin around the ulcer, and adequate arterial blood supply to the ulcer area. Hyperglycaemia (high blood sugar levels) can decrease fibrinolytic activity, which increases blood viscosity and induces a high coagulation state in people with DM (Creager 2003). The high coagulation state can damage vessel walls and lead to vascular dysfunction, coagulation‐anticoagulation disorders and haemorrheological (blood) disturbances (Mekkes 2003). This high coagulation state contributes to the slow healing of diabetic foot ulcers..

There are five criteria that are commonly considered to be the most relevant when grading diabetic foot ulcers, namely: perfusion; extent/size; depth/tissue loss; infection; and sensation. Grading systems score an ulcer in terms of either presence or absence, or severity, for each of these criteria. For instance, the Wagner grading system has five grades based on the severity of infection: Grade 1 ‐ superficial diabetic ulcer; Grade 2 ‐ ulcer extension; Grade 3 ‐ deep ulcer with abscess or osteomyelitis; Grade 4 ‐ gangrene to portion of forefoot; and Grade 5 ‐ extensive gangrene of foot (Wagner 1987).

Diabetic foot ulcers are a significant personal health issue for those who have them, and are associated with a considerable economic burden that impacts significantly on healthcare systems. In the USA, the costs of diabetic foot ulcers were estimated as US $40 billion each year. When compared with a person who has DM but no foot ulcer, the cost of diabetic patients with a foot ulcer is 5.4 times higher in the year after the first ulcer episode, and 2.8 times higher in the second year. Costs for the treatment of the highest‐grade ulcers are eight times higher than for low‐grade ulcers (Cavanagh 2012; Driver 2010).

Description of the intervention

There are multiple approaches to treating foot ulcers in people with DM that include: glycaemic (blood sugar level) control; diet control; standard care for ulcers; correction of arterial insufficiency; resection of the chronic wound (ulcer); and the use of wound dressings (Game 2012). In 2012, guidelines from the IWGDF recommended that the main principles of ulcer treatment should be: 1) relief of pressure and protection of the ulcer; 2) restoration of skin perfusion; 3) treatment of infection; 4) metabolic control and treatment of comorbidity; and 5) local wound care (Bakker 2012b).

Heparin and heparin‐related (i.e. 'related') substances are glycosaminoglycans (GAGs); these are polysaccharides whose classification is based on core disaccharide (two sugar) groups that repeat. Heparin is a GAG of mixed composition, i.e. molecules of different lengths. It has potent anticoagulant properties that are used to treat and prevent clotting disorders where there is excessive or undesirable clotting, including, thrombophlebitis (clot in vein), acute myocardial infarction (heart attack), stroke, and pulmonary embolism (clot in lung). Heparins can be separated into two groups: unfractionated heparin (UFH) (heparin in a range of molecular sizes), and low‐molecular‐weight heparin (LMWH) (smaller heparin molecules). Both these are potent antithrombotic (anti‐clotting) agents that also enhance fibrinolytic activity and have anti‐inflammatory effects. UFH is a naturally‐occurring polysaccharide that works as an anticoagulant by inhibiting the activity of several blood coagulation factors. Laboratory work has shown that heparin‐induced precipitation of low‐density lipoprotein in the blood causes a reduction in the levels of fibrinogen (a clotting agent). This effect, if transferable to people, could lead to the confining of necrotic tissue and a reduction in the amputation rate in people with severe diabetic foot syndrome (Rietzsch 2008). Studies have claimed that heparin can improve haemorrheological parameters, increase arterial blood supply and enhance healing in patients with diabetic foot ulcers (Bonnie 2011; Li 2002). LMWHs consist of short chains of polysaccharide, obtained from various methods of fractionation (separation) or enzymatic depolymerization (cutting) of UFH (Linhardt 1999). LMWH has advantages for the treatment of diabetic foot ulcers compared to UFH. Firstly, LMWH has more favourable bioavailability and pharmacokinetics, so it can be administered subcutaneously without monitoring. Secondly, LMWH may result in fewer bleeding complications due to a less pronounced effect on platelet function and vascular permeability (Hirsh 2001), which means that it can be used long‐term as an out‐of‐hospital treatment because of its relative safety. Subcutaneous injection of dalteparin, one type of LMWH, can improve the capillary circulation in the ulcer margin, which positively influences the healing process of chronic foot ulcers in diabetic patients (Jorneskog 1993). Rullan indicated that diabetic foot ulcers treated with bemiparin, another LMWH preparation, administered once daily by subcutaneous injection were observed to have better ulcer improvement rates, complete healing rates and few adverse reactions (Rullan 2008).

LMWHs are a class of anticoagulants that includes enoxaparin, nadroparin, dalteparin, tinzaparin, bemiparin, and reviparin. Related substances include: chondroitin, heparitin sulphate, hyaluronic acid and keratan sulphate. Chondroitin is a GAG composed of a chain of alternating sugars, usually attached to proteins, as part of a proteoglycan. Heparitin sulphate is a polysaccharide containing the same repeating disaccharide groups as heparin. Hyaluronic acid is a GAG distributed widely throughout connective, epithelial, and neural tissues. Keratan sulphate is, like other GAGs, a linear polymer that consists of a repeating disaccharide unit; it is found especially in the cornea, cartilage, and bone.

How the intervention might work

Heparin and related substances are GAGs that exist naturally inside the cell and in the extracellular matrix (fluid outside cells). They act by binding selectively to varieties of proteins and pathogens (disease‐causing agents) and are crucially relevant to many disease processes (Gandhi 2010; Shafritz 1994).They have beneficial effects on local tissue microcirculation and oxygenation through the inhibition of thrombin generation and increases in plasma fibrin gel porosity, which may promote vascular perfusion in the ischaemic foot significantly and lead to improvements in its blood supply. They can promote healing of chronic ulcers by stimulating production of basic fibroblast growth factor and transforming growth factor‐beta 1 (Carroll 2003). Laboratory work has also shown that they have positive effects in vitro, including promotion of the synthesis of heparin sulphate in endothelial cell cultures (Cavanagh 2012), and the proliferation of fibroblasts (cells involved in wound healing) obtained from diabetic ulcers (Warren 2009). Heparin can promote neo vascularisation (growth of new blood vessels) in ischaemic limbs by improving the structure and number of capillaries (Bakker 2012b; Game 2012). All these activities mean that heparin and related substances might act as a scaffold to enhance the activity of growth factors and reduce the inflammatory response in the ulcer bed.

Why it is important to do this review

Some published studies have demonstrated positive effects for heparin and related substances on the healing of diabetic foot ulcers (Kalani 2003; Rullan 2008), but most of these have methodological limitations. As far as we know, there are, as yet, no systematic reviews addressing this topic. Consequently, a systematic review of the available evidence for the efficacy and safety of heparin and related substances for diabetic foot ulcers is required.

Objectives

To assess the efficacy and safety of heparin and heparin‐related substances for the treatment of diabetic foot ulcers.

Methods

Criteria for considering studies for this review

Types of studies

Published or unpublished randomised controlled trials (RCTs) and quasi‐RCTs.

Types of participants

Inclusion criteria

• People with type 1 or type 2 DM with foot ulcers. There will be no restriction in relation to the aetiology of the ulcer; trials may concern ulcers that are neuropathic, Ischaemic or neuroischaemic.

• Diagnosis of DM: according to the American Diabetes Association, Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus (ADA 1997) (i.e. fasting plasma glucose ≥ 7.0 mmol/L, and two hour plasma glucose ≥ 11.1 mmol/L).

• People with diabetic foot ulcers can be of any age or gender, and have an ulcer of any level of severity.

Exclusion criteria

• Foot ulcers due to types of diabetes other than type 1 or type 2 (e.g. gestational, secondary).

• Foot ulcers due to diseases other than DM (e.g. pressure, venous, and arterial ulcers).

Types of interventions

Any heparin or heparin‐related substance, including LMWH, chondroitin, heparitin sulphate, hyaluronic acid and keratan sulphate, used for treating foot ulcers in people with diabetes, regardless of dosage, routes of administration or duration of treatment. We will make the following comparisons:

• heparin or a related substance compared with placebo or conventional therapy;

• heparin or a related substance versus another heparin or related substance.

Conventional therapy will include standard care for foot ulcers as defined by the trial authors.  

Types of outcome measures

Primary outcomes

• Proportion of people whose ulcers have healed completely within the trial period by the end of treatment.

• Proportion of people whose ulcers have healed completely in the trial period by the end of follow‐up (trial period).

• Time to complete healing, or reduced size at end of treatment.

• Change in area of ulcer within a specific time period (the period of time will be the duration of the study unless otherwise stated).

Secondary outcomes

• Amputation at the end of follow‐up.

• Glycaemic control (HbA1c %) at the end of treatment.

• Level of plasma fibrinogen at the end of treatment.

• Level of plasma viscosity at the end of treatment.

• Quality of life (measured using a standardised generic questionnaire such as EQ‐5D, SF‐36, SF‐12 or SF‐6 or disease‐specific questionnaire) at the end of follow‐up (Hurst 1994).

• Adverse events: any kind of adverse events reported in the trials will be assessed at end of treatment.

Search methods for identification of studies

We will not restrict the search by date, language or publication status of articles.

Electronic searches

We will search the following electronic databases to identify reports of relevant randomised clinical trials:

• Cochrane Wounds Group's Specialised Register (most recent version);

• Cochrane Central Register of Controlled Trials (CENTRAL) (latest issue);

• MEDLINE (Ovid SP) (1946 to present);

• EMBASE (Ovid SP) (1974 to present);

• CINAHL (EBSCO) (1982 to present);

• Chinese Biomedical Literature Database (CBM) (1978 to present);

• VIP Chinese Science and Technique Journals Database (1989 to present);

• China National Knowledge Infrastructure (CNKI) Database (1979 to present);

• Wan Fang database (1986 to present).

We will use the following provisional search strategy in The Cochrane Central Register of Controlled Trials (CENTRAL):

#1 MeSH descriptor Glycosaminoglycans explode all trees #2 mucopolysaccharide*:ti,ab,kw #3 (chondroitin or dermatan* or heparin* or LMWH or "hyaluronic acid" or dalteparin or tedelparin or kabi2165 or "kabi 2165" or kabi‐2165 or fragmin or FR860 or "FR 860" or FR‐860 or nadroparin* or fraxiparin* or CY216 or "CY 216" or CY‐216or enoxaparin or PK10169 or "PK 10169" or PK‐10169 or EMT967 or "EMT 967" or EMT‐967 or lovenox or clexane or EMT966 or "EMT 966" or EMT‐966 or ardeparin or normiflo or wy90493 or "wy 90493" or wy‐90493 or bemiparin or certoparin or mono‐embolex or alphaparin or sandoparin or danaproid or lomoparan or org10172 or "org 10172" or org‐10172 or orgaran or fondaparinux or quixidar or arixtra or idraparinux or parnaparin or CB‐01‐05‐MMX or fluxum or parvoparin or tinzaparin or innohep or Logiparin or reviparin* or LU47311 or "LU 47311" or LU‐47311 or Clivarin* or galactosaminoglycan* or perlecan or "polysialic acid" or proteoheparan* or sulodexide* or syndecan or trichosaccaride*):ti,ab,kw #4 (keratan NEXT (sulfate* or sulphate*)):ti,ab,kw #5 (1 OR 2 OR 3 OR 4) #6 MeSH descriptor Foot Ulcer explode all trees #7 MeSH descriptor Diabetic Foot explode all trees #8 (diabet* NEAR/5 ulcer*):ti,ab,kw #9 (diabet* NEAR/5 (foot or feet)):ti,ab,kw #10 (diabet* NEAR/5 wound*):ti,ab,kw #11 (6 OR 7 OR 8 OR 9 OR 10) #12 (5 AND 11) We will adapt this strategy to search Ovid MEDLINE, Ovid EMBASE and EBSCO CINAHL. We will combine the Ovid MEDLINE search with the Cochrane Highly Sensitive Search Strategy for identifying randomised trials in MEDLINE: sensitivity‐ and precision‐maximising version (2008 revision) (Lefebvre 2011). We will combine the EMBASE search with the Ovid EMBASE filter developed by the UK Cochrane Centre (Lefebvre 2011). We will combine the CINAHL searches with the trial filters developed by the Scottish Intercollegiate Guidelines Network (SIGN 2014). We will not restrict studies with respect to language, date of publication or study setting.

We will search the following clinical trials registries:

• ClinicalTrials,gov (http://www.clinicaltrials.gov/)

• WHO International Clinical Trials Registry Platform (http://apps.who.int/trialsearch/Default.aspx)

• EU Clinical Trials Register (https://www.clinicaltrialsregister.eu/)

Searching other resources

• The bibliographies of relevant RCTs identified through the above electronic searches will be scanned for additional studies.

• Relevant manufacturers will be contacted to identify unpublished data/studies.

• We will follow up RCTs mentioned as having being started as a result of published pilot study results.

Data collection and analysis

Selection of studies

Two review authors (TX, NS) will independently screen the titles and abstracts retrieved from the search . Then they will obtain copies of the full text articles that appear to be potentially relevant, and will assess them in further detail. Any disagreements will be resolved through discussion.

Data extraction and management

Independently, two review authors (LD, NS) will extract data from the primary publications and from any associated online appendices using a standardised data extraction form. This extraction form will include the following data.

• Source (study ID; contact details).

• Eligibility (confirm eligibility for review; reason(s) for exclusion).

• Methods (study design; total study duration; sequence generation; allocation sequence concealment; blinding; other concerns about bias).

• Participants (total number; setting; diagnostic criteria; age; sex; country; date of study).

• Interventions (total number of intervention groups; intervention details).

• Outcomes (outcomes and time points; outcome definition).

• Results (number of participants allocated to each intervention group; missing participants).

• Miscellaneous (funding source).

One review author (BW) will check and enter the data directly into Review Manager 5.2 software for statistical analysis (RevMan 2011). Another review author (LD) will check the data after entry into RevMan to detect entry errors.

Assessment of risk of bias in included studies

Independently, two review authors (LD, NS) will assess each included study based on the Cochrane Collaboration risk of bias tool (Higgins 2011) (see Appendix 2). This will include the following items.

• Random sequence generation.

• Allocation concealment.

• Blinding of participants and personnel.

• Blinding of outcome assessment.

• Incomplete outcome data.

• Selective reporting.

• Other bias.

Measures of treatment effect

There may be three categories of outcome data: dichotomous (or binary) data, continuous data, and time‐to‐event data. We will present the outcome results for each trial with 95% confidence intervals (CI) and will define measures of treatment effects as follows.

Dichotomous (or binary) data

We will report estimates for dichotomous data (e.g. ulcer healing rates, adverse events) as risk ratios (RR) with 95% CI.

Continuous data

We will report estimates for continuous data (e.g. change in area of ulcer) as mean differences (MD) with 95% CI or, if different scales have been used, standardised mean differences (SMD) with 95% CI.

Time‐to‐event data

We will report estimates for time‐to‐event data (e.g. time to ulcer healing) as hazard ratios (HR) with 95% CI.

Unit of analysis issues

We will define an ulcer, a foot, a participant or whether multiple ulcers on the same participant as being the unit of analysis. We will record this as part of the risk of bias assessment.

Dealing with missing data

We will contact study authors if data are missing and request that they provide them; we will include any relevant data obtained in this manner in the review. For binary outcomes in trials without ITT analysis, we will seek the number of participants from the trial, and assume that any missing participants did not heal.

Assessment of heterogeneity

We will consider clinical heterogeneity (that is the degree to which studies vary in terms of participant, intervention and outcome characteristics). Statistical heterogeneity will be evaluated using the Chi² test (in which P values less than 0.1 will be considered to indicate significant heterogeneity). Statistics for quantifying heterogeneity across studies will be evaluated using the I² test. A rough guide to interpretation of this test is as follows (Higgins 2011):

• 0% to 40%: might not be important;

• 30% to 60%: may represent moderate heterogeneity;

• 50% to 90%: may represent substantial heterogeneity;

• 75% to 100%: represents considerable heterogeneity.

Assessment of reporting biases

If at least 10 RCTs are included in the review, we will try to estimate reporting biases by using a funnel plot.

Data synthesis

We will analyse the data using RevMan (version 5.2). If there is little heterogeneity (i.e. I² is less than or equal to 40%), we will summarise our findings using a fixed‐effect model, but if there is a high level of statistical heterogeneity (i.e. I² exceeds 40%), we will consider using a random‐effects model, or we will not undertake pooling and present the findings of the trial in the narrative. We will explore possible reasons for both clinical and statistical heterogeneity and comment on them.

Subgroup analysis and investigation of heterogeneity

Should data be available, potential subgroup analyses will be:

• different types of heparin and related substances (heparin, LMWH, chondroitin, heparitin sulphate, hyaluronic acid and keratan sulphate).

• different doses of heparin and heparin related substances.

• different durations of treatment.

Presence of statistical heterogeneity will be taken into account in interpretation of sub‐group analysis results.

Sensitivity analysis

If sufficient information and data are available, we will perform the following sensitivity analyses and repeat the analysis to explore the influence of:

• all unpublished studies (if there are any);

• all trials at high risk of bias for random sequence generation (if there are any);

• all trials at high risk of bias for allocation concealment (if there are any);

• all trials at high risk of bias for missing data (if there are any).

Appendices

Appendix 1. Electronic search strategies

Database	Search terms
CENTRAL	1. MeSH descriptor Glycosaminoglycans explode all trees 2. mucopolysaccharide*:ti,ab,kw 3. (chondroitin or dermatan* or heparin* or LMWH or "hyaluronic acid" or dalteparin or tedelparin or kabi2165 or "kabi 2165" or kabi‐2165 or fragmin or FR860 or "FR 860" or FR‐860 or nadroparin* or fraxiparin* or CY216 or "CY 216" or CY‐216or enoxaparin or PK10169 or "PK 10169" or PK‐10169 or EMT967 or "EMT 967" or EMT‐967 or lovenox or clexane or EMT966 or "EMT 966" or EMT‐966 or ardeparin or normiflo or wy90493 or "wy 90493" or wy‐90493 or bemiparin or certoparin or mono‐embolex or alphaparin or sandoparin or danaproid or lomoparan or org10172 or "org 10172" or org‐10172 or orgaran or fondaparinux or quixidar or arixtra or idraparinux or parnaparin or CB‐01‐05‐MMX or fluxum or parvoparin or tinzaparin or innohep or Logiparin or reviparin* or LU47311 or "LU 47311" or LU‐47311 or Clivarin* or galactosaminoglycan* or perlecan or "polysialic acid" or proteoheparan* or sulodexide* or syndecan or trichosaccaride*):ti,ab,kw 4. (keratan NEXT (sulfate* or sulphate*)):ti,ab,kw 5. (1 OR 2 OR 3 OR 4) 6. MeSH descriptor Foot Ulcer explode all trees 7. MeSH descriptor Diabetic Foot explode all trees 8. (diabet* NEAR/5 ulcer*):ti,ab,kw 9. (diabet* NEAR/5 (foot or feet)):ti,ab,kw 10. (diabet* NEAR/5 wound*):ti,ab,kw 11. (6 OR 7 OR 8 OR 9 OR 10) 12. (5 AND 11)
MEDLINE	1. exp Glycosaminoglycans/ 2. mucopolysaccharide*.tw. 3. (chondroitin or dermatan* or heparin* or LMWH or hyaluronic acid or dalteparin or tedelparin or kabi?2165 or fragmin or FR?860 or nadroparin* or fraxiparin* or CY?216 or enoxaparin or PK?10169 or EMT?967 or lovenox or clexane or EMT?966 or ardeparin or normiflo or wy?90493 or bemiparin or certoparin or mono‐embolex or alphaparin or sandoparin or danaproid or lomoparan or org?10172 or orgaran or fondaparinux or quixidar or arixtra or idraparinux or parnaparin or CB‐01‐05‐MMX or fluxum or parvoparin or tinzaparin or innohep or Logiparin or reviparin* or LU?47311 or Clivarin* or galactosaminoglycan* or perlecan or polysialic acid or proteoheparan* or sulodexide* or syndecan or trichosaccaride*).tw. 4. (keratan adj (sulfate* or sulphate*)).tw. 5. or/1‐4 6. exp Foot Ulcer/ 7. exp Diabetic Foot/ 8. (diabet* adj3 ulcer*).tw. 9. (diabet* adj3 (foot or feet)).tw. 10. (diabet* adj3 wound*).tw. 11. or/6‐10 12. (5 and 11)

Appendix 2. Tool for assessing risk of bias

Tool for assessing risk of bias	Assessment criteria
Random sequence generation	'Low risk' of bias: referring to a random number table; using a computer random number generator; coin tossing; shuffling cards or envelopes; throwing dice; drawing of lots; minimisation*. *Minimization may be implemented without a random element, and this is considered to be equivalent to being random.
	'High risk' of bias: sequence generated by odd or even date of birth; sequence generated by some rule based on date (or day) of admission; sequence generated by some rule based on hospital or clinic record number; allocation determined by judgement of the clinician; allocation determined by preference of the participant; allocation based on the results of a laboratory test or a series of tests; allocation determined by availability of the intervention.
	'Unclear risk' of bias: insufficient information about the sequence generation process to permit judgement of 'Low risk' or 'High risk'.
Allocation concealment	'Low risk' of bias: central allocation (including telephone, web‐based and pharmacy‐controlled randomisation); sequentially‐numbered drug containers of identical appearance; sequentially‐numbered, opaque, sealed envelopes.
	'High risk' of bias: using an open random allocation schedule (e.g. a list of random numbers); using assignment envelopes without appropriate safeguards (e.g. if envelopes were unsealed or non­opaque or not sequentially numbered); alternation or rotation; date of birth; case record number; any other explicitly unconcealed procedure.
	'Unclear risk' of bias: insufficient information to permit judgement of 'Low risk' or 'High risk'.
Blinding of participants and personnel	'Low risk' of bias: no blinding or incomplete blinding, but the review authors judge that the outcome is not likely to be influenced by lack of blinding; blinding of participants and key study personnel ensured, and unlikely that the blinding could have been broken.
	'High risk' of bias: no blinding or incomplete blinding, and the outcome is likely to be influenced by lack of blinding; blinding of key study participants and personnel attempted, but likely that the blinding could have been broken, and the outcome is likely to be influenced by lack of blinding.
	'Unclear risk' of bias: insufficient information to permit judgement of 'Low risk' or 'High risk'; the study did not address this outcome.
Blinding of outcome assessment	'Low risk' of bias: no blinding of outcome assessment, but the review authors judge that the outcome measurement is not likely to be influenced by lack of blinding; blinding of outcome assessment ensured, and unlikely that the blinding could have been broken.
	'High risk' of bias: no blinding of outcome assessment, and the outcome measurement is likely to be influenced by lack of blinding; blinding of outcome assessment, but likely that the blinding could have been broken, and the outcome measurement is likely to be influenced by lack of blinding.
	'Unclear risk' of bias: insufficient information to permit judgement of 'Low risk' or 'High risk'; the study did not address this outcome.
Incomplete outcome data	'Low risk' of bias: no missing outcome data; reasons for missing outcome data unlikely to be related to true outcome (for survival data, censoring unlikely to be introducing bias); missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups; for dichotomous outcome data, the proportion of missing outcomes compared with observed event risk is not enough to have a clinically relevant impact on the intervention effect estimate; for continuous outcome data, plausible effect size (difference in means or standardised difference in means) among missing outcomes is not enough to have a clinically relevant impact on observed effect size; missing data have been imputed using appropriate methods.
	'High risk' of bias: reason for missing outcome data likely to be related to true outcome, with either imbalance in numbers or reasons for missing data across intervention groups; for dichotomous outcome data, the proportion of missing outcomes compared with observed event risk is enough to induce clinically relevant bias in intervention effect estimate; for continuous outcome data, plausible effect size (difference in means or standardised difference in means) among missing outcomes enough to induce clinically relevant bias in observed effect size; 'as‐treated' analysis done with substantial departure of the intervention received from that assigned at randomisation; potentially inappropriate application of simple imputation.
	'Unclear risk' of bias: insufficient reporting of attrition/exclusions to permit judgement of 'Low risk' or 'High risk' (e.g. number randomised not stated, no reasons for missing data provided); the study did not address this outcome.
Selective reporting	'Low risk' of bias: the study protocol is available and all of the study's pre‐specified (primary and secondary) outcomes that are of interest in the review have been reported in the pre‐specified way; the study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified (convincing text of this nature may be uncommon).
	'High risk' of bias: not all of the study's pre‐specified primary outcomes have been reported; one or more primary outcomes are reported using measurements, analysis methods or subsets of the data (e.g. subscales) that were not pre‐specified; one or more of the reported primary outcomes were not pre‐specified (unless clear justification for their reporting is provided, such as an unexpected adverse effect); one or more outcomes of interest in the review are reported incompletely so that they cannot be entered in a meta‐analysis; the study report fails to include results for a key outcome that would be expected to have been reported for such a study.
	'Unclear risk' of bias: insufficient information to permit judgement of 'Low risk' or 'High risk'. It is likely that the majority of studies will fall into this category.
Other sources of bias	'Low risk' of bias: the study appears to be free of other sources of bias.
	'High risk' of bias: the study has a potential source of bias related to the specific study design used; has been claimed to have been fraudulent; had some other problem.
	'Unclear risk' of bias: insufficient information to assess whether an important risk of bias exists; insufficient rationale or evidence that an identified problem will introduce bias.

What's new

Date	Event	Description
11 December 2017	Amended	This protocol has been withdrawn as authors were unable to progress the review.

Contributions of authors

TX: developed and co‐ordinated the protocol, made an intellectual contribution to the protocol, and approved the final version of the protocol prior to submission. NS: performed part of the writing and editing of the protocol, and made an intellectual contribution to the protocol. NT: advised on part of the protocol, provided clinical knowledge, and made an intellectual contribution to the protocol. LD: developed and ran the search strategy, and made an intellectual contribution to the protocol. BW: edited part of the protocol, and made an intellectual contribution to the protocol.

Contributions of editorial base:

Liz McInnes, Editor: advised on methodology, interpretation and protocol content. Approved the final protocol prior to submission. Sally Bell‐Syer: coordinated the editorial process. Advised on methodology, interpretation and content. Edited the protocol. Ruth Foxlee: designed the search strategy and edited the search methods section.

Sources of support

Internal sources

• Chinese Cochrane Center, China.

External sources

• The National Institute for Health Research (NIHR) is the sole funder of the Cochrane Wounds Group, UK.

Declarations of interest

TX: none known. NS: none known. NT: none known. LD: none known. BW: none known.

Notes

This protocol has been withdrawn as authors were unable to progress the review.

Withdrawn from publication for reasons stated in the review