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, humid environments, people with absence of ear wax or with narrow ear canals, hearing-aid users, and after mechanical trauma.

Methods and outcomes

We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of empirical and prophylactic treatments for otitis externa? We searched: Medline, Embase, The Cochrane Library, and other important databases up to October 2007 (Clinical Evidence reviews are updated periodically; please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).

Results

We found nine systematic reviews, RCTs, or observational studies that met our inclusion criteria. 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 drops or spray, topical aluminium acetate drops, topical antibacterials, topical antifungals, topical anti-infective agents, topical corticosteroids, and water exclusion.

Key Points

Otitis externa is thought to affect 10% of people at some stage, and can present as acute, chronic, or necrotising forms.

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

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

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

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.

Consensus suggests thattopical 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.

We don't know whether topical antifungal agents or specialist aural toilet improve symptoms of otitis externa.

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 media when used with topical anti-infective agents and corticosteroids, but is less effective when used alone.

Prophylactic treatments to prevent otitis externa (topical acetic acid, topical corticosteroids, and water exclusion) have not been evaluated in clinical trials.

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 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. Acute otitis externa may present as a single episode, or may recur. 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) 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. In this review, we look at the empirical treatment of only acute and chronic otitis externa.

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 local or generalised eczema of the ear canal. It is more common in swimmers, humid environments, people with an absence of ear wax or narrow external ear canals, hearing-aid users, and after mechanical trauma.

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; adverse effects of treatment.

Methods

Clinical Evidence search and appraisal October 2007. The following databases were used to identify studies for this review: Medline 1966 to October 2007, Embase 1980 to October 2007, and The Cochrane Database of Systematic Reviews and Cochrane Central Register of Controlled Clinical Trials 2007, Issue 3. Additional searches were carried out using these websites: NHS Centre for Reviews and Dissemination (CRD) — for Database of Abstracts of Reviews of Effects (DARE) and Health Technology Assessment (HTA), Turning Research into Practice (TRIP), and NICE. Abstracts of the studies retrieved from the initial search were assessed by an information specialist. Selected studies were then sent to the author for additional assessment, using predetermined criteria to identify relevant studies. Study design criteria for inclusion in this review were: published systematic reviews and RCTs in any language, at least single blinded, and containing more than 20 individuals of whom more than 80% were followed up. The minimum length of follow-up required to include studies was one month. We excluded all studies described as “open”, “open label”, or not blinded unless blinding was impossible. In addition, we use a regular surveillance protocol to capture harms alerts from organisations, such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA), which are added to the review as required. 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 drops versus topical antibacterial–corticosteroid	4	–2	0	0	0	Low	Quality points deducted for sparse data and lack of power to detect clinically important differences between groups
1 (40)	Symptom improvement	Topical antibacterial–corticosteroids versus placebo	4	–1	0	0	0	Moderate	Quality point deducted for sparse data.
3 (1465)	Cure rate	Topical antibacterials (with or without corticosteroids) versus each other	4	–1	–1	–1	0	Very low	Quality point deducted for incomplete reporting of results. Consistency point deducted for conflicting results among studies. Directness point deducted for inconsistent comparators
1 (60)	Cure rate	Topical antibacterial–corticosteroid–acetic acid versus topical antibacterial–corticosteroid alone	4	–1	0	0	0	Moderate	Quality point deducted for sparse data.
1 (53)	Cure rate	Topical antibacterial–corticosteroid–acetic acid versus topical acetic acid alone	4	–1	0	0	0	Moderate	Quality point deducted for sparse data
1 (138)	Cure rate	Topical acetic acid versus topical antibacterial–corticosteroid	4	–1	0	0	+1	High	Quality point deducyed for sparse data. Effect size point added for odds ratio of 2–5
1 (138)	Symptom improvement	Topical acetic acid versus topical antibacterial–corticosteroid	4	–1	0	0	0	Moderate	Quality point deducted for sparse data
1 (138)	Recurrence	Topical acetic acid versus topical antibacterial–corticosteroid	4	–1	0	0	+1	High	Quality point deducted for sparse data. Effect-size point added for odds ratio of 0.2–0.5
1 (126)	Cure rate	Topical acetic acid versus topical acetic acid–corticosteroid	4	–1	0	0	+1	High	Quality point deducted for sparse data. Effect-size point added for odds ratio of 2 to 5
1 (126)	Symptom improvement	Topical acetic acid versus topical acetic acid–corticosteroid	4	–1	0	0	0	Moderate	Quality point deducted for sparse data
1 (104)	Recurrence	Topical acetic acid versus topical acetic acid–corticosteroid	4	-1	0	0	+1	High	Quality point deducted for sparse data. Effect-size point added for odds ratio of 0.2 to 0.5
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

High-quality evidence

Further research is very unlikely to change our confidence in the estimate of effect.

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.

Very low-quality evidence

Any estimate of effect is very uncertain.

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