Antibiotics for acute otitis externa
- Systematic review
- Results
- Comment
Acute
otitis externa is an inflammation of the external ear canal, commonly known as
swimmer's ear. It can be treated with systemic or topical antibiotics,
and topical treatment can involve several different types of antibiotic or
antiseptic, sometimes combined with cortiocosteroid. A systematic review
reveals just how little we know about what works best [1].
Systematic
review
Searching
involved using different databases for studies in any language. Articles were
limited to acute otitis externa, parallel group design, and comparing
antimicrobial and placebo, antiseptic and antimicrobial, and steroid plus
antimicrobial versus antimicrobial alone or steroid alone. Outcomes used
included clinical cure (absence of all signs and symptoms) or improvement
(partial or complete relief). Different end points over 3 to 21 days were
examined, with the intention to combine the final results.
Results
Twenty
trials described as randomised were found, 18 with the required information for
data pooling. The median size was 79 patients (range 28 to 842), all but one
including children and adults. Half did not explicitly define acute otitis
externa, and only half were defined as double blind.
Using
the Oxford quality scoring system for randomisation, blinding, and withdrawal
description, only 10 scored 3 out of 5 points, associated with a relative lack
of bias. Those that were adequate (3, 4, or 5 out of 5) did not improve with
time (Table 1).
Table 1: Trial quality over five decades
|
Quality score
(range 1-5)
|
| Decade |
1 or 2
|
3-5
|
| 1960s |
0
|
1
|
| 1970s |
1
|
3
|
| 1980s |
1
|
1
|
| 1990s |
4
|
2
|
| 2000s |
4
|
3
|
There
were 13 meta-analyses of these 18 trials, without sensitivity analysis
according to quality score. The effect of topical antibiotic (neomycin) plus
corticosteroid compared with placebo was described in only two good quality
studies, with only 89 patients. Cure rates were much higher for antibiotic plus
steroid than with placebo at 3-10 days. The NNT calculated for these two trials
was 2.2 (1.6 to 3.7).
The
only other comparisons of at least two treatments with relatively unbiased
trials was for antiseptic versus antibiotic in three trials, with identical
cure rates of about 60% at 7-10 days and 80% at 14 to 28 days.
Comment
Another
example where we have a paucity of data to guide therapy for a relatively
common condition. Most trials were performed since 1990, yet most had poor
quality scores indicating at best poor reporting quality, and at worse
inadequate conduct. If anything, the quality of more recent trials was worse
than those published earlier (Table 1). These are simple trials, and the
influence of quality is well known. How can it be that trials of inadequate
quality continue to be performed or reported? This shows a clear failure by
ethics committees and journals, and a disservice to patients and professionals.
Reference:
- 1 RM Rosenfeld et al. Systematic review of topical antimicrobial therapy for acute otitis externa. Otolaryngology – Head and Neck Surgery 2006 134:S24-S48.
