Otitis externa

Abstract

Introduction

Otitis externa is thought to affect 10% of people at some stage, and can present in acute, chronic, or necrotising forms. Otitis externa may be associated with eczema of the ear canal, and is more common in swimmers, in humid environments, in people with narrow ear canals, in hearing-aid users, and after mechanical trauma.

Methods and outcomes

We conducted a systematic review and aimed to answer the following clinical question: What are the effects of empirical treatments for otitis externa? We searched: Medline, Embase, The Cochrane Library, and other important databases up to October 2013 (BMJ Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review).

Results

Nine studies were included. We performed a GRADE evaluation of the quality of evidence for interventions.

Conclusions

In this systematic review, we present information relating to the effectiveness and safety of the following interventions: oral antibiotics, specialist aural toilet, topical acetic acid, topical aluminium acetate, topical antibacterials, topical antifungals, topical corticosteroids, and combinations of these agents.

Key Points

Otitis externa is thought to affect 10% of people at some stage, and can present as acute, chronic, or necrotising forms. While milder forms of acute otitis externa are often short-lived isolated episodes, a substantial proportion of cases can persist for weeks or even months, despite intensive treatment. Once resolved, there is a significant risk of recurrence. Because of the risk of chronicity or recurrence, we have excluded studies with follow-up periods of less than 1 month; optimal treatment should not just transiently suppress early symptoms.

• Otitis externa may be associated with eczema or psoriasis of the ear canal or conchal bowl. It is more common in swimmers, in humid environments, in people with narrow ear canals, in hearing-aid users, and after mechanical trauma or ear syringing.

• The most common pathogens are Pseudomonas aeruginosa and Staphylococcus aureus.

• Fungal overgrowth can occur, especially after prolonged antibiotic use.

Topical aluminium acetate may be as effective as a topical antibacterial-corticosteroid at improving cure rates in people with acute otitis externa.

Topical antibacterial agents are likely to improve signs and symptoms of otitis externa.

• Combining topical antibacterial agents and corticosteroids (methylprednisolone-neomycin drops) is likely to be more effective than placebo in reducing signs and symptoms of otitis externa over 28 days.

• We don't know whether any one topical antibacterial regimen should be used in preference to another.

There is a lack of evidence for corticosteroids when used alone, however they are likely to be beneficial when used in combination with antibacterials.

• Consensus suggests that topical corticosteroids alone may reduce signs and symptoms of otitis externa, but few good-quality studies have been found assessing these agents alone in this population.

There is a lack of evidence to demonstrate the benefit of specialist aural toilet use in otitis externa despite the fact there is consensus that it is likely to be beneficial and it is a key treatment used in the secondary care setting, particularly in cases where topical therapy alone has failed.

We don't know whether topical antifungal agents improve symptoms of otitis externa. However, consensus would suggest that it is inferior as a first-line empirical agent, given that the most common pathogens implicated are bacterial; although, this may not be the case in tropical climates.

Oral antibiotics have not been shown to be beneficial.

• Consensus suggests that adding oral antibiotics to topical anti-infective agents will not improve symptoms compared with topical agents alone.

Topical acetic acid is likely to increase cure of otitis externa when used with topical anti-infective agents and corticosteroids, but is of unknown effectiveness when used alone.

Preservatives in some topical ear products may potentially cause discomfort or contact dermatitis. Patient choice of generic topical ear drops may, therefore, be informed by the preservative used in a preparation.

Overall, there is a relative lack of high-quality trials to assess each of these treatments, so meta-analysis is often not possible. In general, the outcomes of the various topical treatments available, and their combinations, are similar.

Most of the studies have been performed in a secondary care setting, where aural toilet has also been provided. It is not clear how applicable these findings are to the primary care setting, where most cases of otitis externa are managed.

Clinical context

General background

Otitis externa is a common inflammatory (normally infective) condition affecting the external ear canal. It can usually be treated successfully in the primary care setting with ear drops.

Focus of the review

There is a wide range of available topical preparations used in clinical practice to treat otitis externa, including antiseptic agents, antibiotics, corticosteroids, antifungals, and combinations of these. The main purpose of this review is to identify the evidence base to support the use of these treatments in uncomplicated otitis externa.

Comments on evidence

We found numerous studies on the medical treatment of otitis externa but the majority are of poor quality, underpowered, lack blinding, or have inadequate follow-up to be of clinical value. There are also multiple potential interventions, which are often used in combination, so the evidence available to assess and compare individual interventions is generally limited.

Search and appraisal summary

The update literature search for this review was carried out from the date of the last search, October 2007, to October 2013. For more information on the electronic databases searched and criteria applied during assessment of studies for potential relevance to the review, please see the Methods section. After deduplication and removal of conference abstracts, 38 records were screened for inclusion in the review. Appraisal of titles and abstracts led to the exclusion of 28 studies and the further review of 10 full publications. Of the 10 full articles evaluated, one systematic review was added at this update.

Additional information

This review also considers the improved efficacy of topical agents over oral antibiotics in uncomplicated otitis externa. In addition to topical ear drops, aural toilet (with microsuction or ear mopping) and the use of ear wicks to aid administration of topical therapy in patients with oedematous ear canals constitute common treatment interventions. Aural toilet is usually performed in the secondary care setting, often when topical treatment alone has failed. This treatment practice is included in this review. However, given the methodological difficulties of performing robust trials with a procedural intervention, the evidence is sparse.

About this condition

Definition

Otitis externa is inflammation of the external ear canal, often with infection. This inflammation is usually generalised throughout the ear canal, so it is often referred to as 'diffuse otitis externa'. This review excludes localised inflammations, such as furuncles. Otitis externa has acute (<6 weeks), chronic (>3 months), and necrotising (malignant) forms. While milder forms of acute otitis externa are often short-lived isolated episodes, a substantial proportion of cases can persist for weeks or even months, despite intensive treatment. And, once resolved, there is a significant risk of recurrence. It causes pain with aural discharge and associated hearing loss. If the ear canal is visible, it appears red and inflamed. Pseudomonas aeruginosa and Staphylococcus aureus are the most frequent bacterial pathogens in otitis externa. Fungal overgrowth (e.g., with Aspergillus niger and candida) is also common, especially after prolonged antibiotic treatment. Chronic otitis externa may result in canal stenosis with associated hearing loss, for which it may be difficult to fit hearing aids. Necrotising otitis externa is defined by destruction of the temporal bone, usually in people with diabetes or in people who are immunocompromised, and can be life threatening. Making an accurate diagnosis can be challenging, firstly to differentiate between otitis media and otitis externa (although these may co-exist) and secondly to decide on the most likely underlying cause (e.g., bacterial, fungal, dermatitis), so that the most appropriate treatment can be started. In this review, we look at the empirical treatment of only acute and chronic otitis externa. Topical treatment refers to drops, ointment, solution, cream, or spray. The population studied included adults and children.

Incidence/ Prevalence

Otitis externa is common worldwide. The exact incidence is unknown, but 10% of people are thought to have been affected at some time. The condition does affect children, but is more common in adults. It accounts for a large proportion of the workload in otolaryngology departments, but milder cases are often managed in primary care.

Aetiology/ Risk factors

Otitis externa may be associated with dermatological disease of the ear canal and conchal bowl, such as eczema and, less commonly, psoriasis. It is more common in swimmers, in humid environments, in people with narrow external ear canals, in hearing-aid users, and after mechanical trauma or ear syringing. Many clinicians suggest prophylactic measures for patients with recurrent otitis externa. These include water precautions to keep the ears dry, topical corticosteroids to treat underlying eczema, or regular antiseptic agents (e.g., acetic acid or aluminium acetate) to reduce the pH of the ear canal, thus maintaining an unfavourable milieu for microbes. The rationale for these measures is reasonable, given that moisture and eczema are risk factors for otitis externa. The evidence to determine the efficacy of these practices is, however, lacking and does not form part of this review.

Prognosis

We found few reliable data. Many cases of otitis externa resolve spontaneously over several weeks or months. Acute episodes tend to recur, although risk of recurrence is unknown. Experience suggests that chronic inflammation affects a small proportion of people after a single episode of acute otitis externa and can, rarely, lead to canal stenosis.

Aims of intervention

To improve or abolish symptoms; to prevent recurrence and complications, with minimal adverse effects.

Outcomes

Symptom improvement severity and duration of signs and symptoms (pain, discharge, hearing loss, redness); cure rate defined as complete resolution of signs and symptoms; recurrence; quality of life; and adverse effects.

Methods

Search strategy BMJ Clinical Evidence search and appraisal October 2013. Databases used to identify studies for this systematic review include: Medline 1966 to October 2013, Embase 1980 to October 2013, The Cochrane Database of Systematic Reviews 2013, issue 2 (1966 to date of issue), Database of Abstracts of Reviews of Effects (DARE), and the Health Technology Assessment (HTA) database. Inclusion criteria Study design criteria for inclusion in this review were systematic reviews and RCTs published in English, at least single-blinded, and containing 20 or more individuals (at least 10 per arm), of whom more than 80% were followed up. The minimum length of follow-up required to include studies was 1 month. We decided to exclude studies with a minimum follow up period of less than 1 month because of the risk of the condition becoming chronic and recurrent, meaning that optimal treatment should not simply transiently suppress early symptoms. We excluded all studies described as 'open', 'open label', or not blinded unless blinding was impossible. BMJ Clinical Evidence does not necessarily report every study found (e.g., every systematic review). Rather, we report the most recent, relevant and comprehensive studies identified through an agreed process involving our evidence team, editorial team, and expert contributors. Evidence evaluation A systematic literature search was conducted by our evidence team, who then assessed titles and abstracts, and finally selected articles for full text appraisal against inclusion and exclusion criteria agreed a priori with our expert contributors. In consultation with the expert contributors, studies were selected for inclusion and all data relevant to this overview extracted into the benefits and harms section of the review. In addition, information that did not meet our predefined criteria for inclusion in the benefits and harms section, may have been reported in the 'Further information on studies' or 'Comment' section. Adverse effects All serious adverse effects, or those adverse effects reported as statistically significant, were included in the harms section of the overview. Pre-specified adverse effects identified as being clinically important were also reported, even if the results were not statistically significant. Although BMJ Clinical Evidence presents data on selected adverse effects reported in included studies, it is not meant to be, and cannot be, a comprehensive list of all adverse effects, contraindications, or interactions of included drugs or interventions. A reliable national or local drug database must be consulted for this information. Comment and Clinical guide sections In the Comment section of each intervention, our expert contributors may have provided additional comment and analysis of the evidence, which may include additional studies (over and above those identified via our systematic search) by way of background data or supporting information. As BMJ Clinical Evidence does not systematically search for studies reported in the Comment section, we cannot guarantee the completeness of the studies listed there or the robustness of methods. Our expert contributors add clinical context and interpretation to the Clinical guide sections where appropriate. Data and Quality To aid readability of the numerical data in our reviews, we round many percentages to the nearest whole number. Readers should be aware of this when relating percentages to summary statistics such as relative risks (RRs) and odds ratios (ORs). BMJ Clinical Evidence does not report all methodological details of included studies. Rather, it reports by exception any methodological issue or more general issue which may affect the weight a reader may put on an individual study, or the generalisability of the result. These issues may be reflected in the overall GRADE analysis. We have performed a GRADE evaluation of the quality of evidence for interventions included in this review (see table). The categorisation of the quality of the evidence (high, moderate, low, or very low) reflects the quality of evidence available for our chosen outcomes in our defined populations of interest. These categorisations are not necessarily a reflection of the overall methodological quality of any individual study, because the Clinical Evidence population and outcome of choice may represent only a small subset of the total outcomes reported, and population included, in any individual trial. For further details of how we perform the GRADE evaluation and the scoring system we use, please see our website (www.clinicalevidence.com).

Table.

GRADE Evaluation of interventions for Otitis externa.

Important outcomes	Cure rate , Quality of life, Recurrence , Symptom improvement
Studies (Participants)	Outcome	Comparison	Type of evidence	Quality	Consistency	Directness	Effect size	GRADE	Comment
What are the effects of empirical treatments for otitis externa?
1 (126)	Cure rate	Aluminium acetate (topical) versus antibacterial-corticosteroid (topical)	4	–3	0	0	0	Very low	Quality points deducted for sparse data, lack of clarity on blinding, and lack of power to detect clinically important differences between groups
1 (40)	Symptom improvement	Topical antibacterial-corticosteroids versus placebo	4	–3	0	–1	0	Very low	Quality points deducted for sparse data, unclear method of randomisation, and no definition of otitis externa or exclulsion criteria given; directness point deducted for use of co-intervention (ear cleaning)
1 (38)	Cure rate	Topical antibacterials (with or without corticosteroids) versus each other	4	–2	0	–1	0	Very low	Quality points deducted for sparse data and weak methods; directness point deducted for use of co-intervention (microsuction)
1 (125)	Recurrence	Topical antibacterial-corticosteroid versus topical acetic acid-corticosteroid	4	–2	0	0	0	Low	Quality points deducted for sparse data and no ITT analysis
1 (53)	Cure rate	Topical antibacterial-corticosteroid-acetic acid versus topical acetic acid alone	4	–2	0	–1	0	Very low	Quality points deducted for sparse data and for weak methods; directness point deducted for use of co-intervention (aural toilet)
1 (115)	Recurrence	Topical acetic acid versus topical antibacterial-corticosteroid	4	–2	0	0	+1	Moderate	Quality points deducted for sparse data and no ITT analysis; effect-size point added for odds ratio of >2 to 5
1 (104)	Recurrence	Topical acetic acid versus topical acetic acid-corticosteroid	4	–2	0	0	0	Low	Quality points deducted for sparse data and no ITT analysis
1 (94)	Cure rate	Different types of specialist aural toilet versus each other	4	–1	0	–1	0	Low	Quality point deducted for sparse data; directness point deducted for disparity in active agents used

We initially allocate 4 points to evidence from RCTs, and 2 points to evidence from observational studies. To attain the final GRADE score for a given comparison, points are deducted or added from this initial score based on preset criteria relating to the categories of quality, directness, consistency, and effect size. Quality: based on issues affecting methodological rigour (e.g., incomplete reporting of results, quasi-randomisation, sparse data [<200 people in the analysis]). Consistency: based on similarity of results across studies. Directness: based on generalisability of population or outcomes. Effect size: based on magnitude of effect as measured by statistics such as relative risk, odds ratio, or hazard ratio.

Glossary

Low-quality evidence

Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.

Moderate-quality evidence

Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate.

Specialist aural toilet

Technique (microsuction, non-surgical debridement) used to clear the ear canal, usually performed in a secondary care, specialist setting. It includes dry mopping of the ear canal or suction. This can be performed using a head light or microscope, which allows cleaning of the more medial areas of the ear canal.

Very low-quality evidence

Any estimate of effect is very uncertain.

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