The author concluded that, based on one randomised controlled trial, ear irrigation to remove impacted wax may result in a significant improvement in hearing in a minority of patients, but more evidence is required. The review methods were poorly described and the potential for bias should not be ignored. However, the author's cautious conclusions appear to reflect the limitations of the evidence presented.

To determine if irrigation of the ear to remove impacted wax improves hearing.

The Cochrane Library, MEDLINE, EMBASE and CINAHL were searched for studies published in the English language; the search terms were reported. Papers that had anonymous authors and papers classified as letters or editorials were excluded.

Study designs of evaluations included in the review

Randomised controlled trials (RCTs), quasi-randomised controlled trials and non-randomised comparative studies were eligible for inclusion. Although controlled, two of the included studies did not use an appropriate control group and data were used from the intervention arm only.

Specific interventions included in the review

Studies that compared irrigation of the ear with no treatment or any other method of impacted wax removal were eligible for inclusion. None of the included studies compared ear irrigation with another method of wax removal. No further details of the interventions were provided.

Participants included in the review

Studies of adults with impacted ear wax were eligible for inclusion. Studies that only involved children were excluded. Two of the included studies only included patients with complete occlusion of the tympanic membranes or of the ear canal. The patients were drawn from a variety of settings, including primary care, residential care, a non-intensive care unit in a hospital, and an ear, nose and throat out-patient clinic. One study included patients with moderate to severe high-frequency sensorineural hearing loss. Two studies used patients without ear impaction as controls. Where reported, the participants were mostly aged 60 years or older.

Outcomes assessed in the review

Studies that objectively measured hearing before and after ear irrigation were eligible for inclusion. The review also assessed any other commonly presenting symptoms and adverse events. In the included studies, hearing was measured using pure tone audiometry or an audioscope.

How were decisions on the relevance of primary studies made?

The author did not state how the papers were selected for the review, or how many reviewers performed the selection.

The author did not report any formal assessment of validity. However, aspects of methodological quality such as the blinding of the audiometry test operator, selection bias, statistical power and comparability of the treatment groups were noted in the text.

The author did not state how the data were extracted for the review, or how many reviewers performed the data extraction. Where possible for each study, data on improved hearing for individuals or by ear were extracted with a measure of variance (confidence intervals, CIs, or standard deviations, SDs) and the number-needed-to-treat (NNT) to see one clinically significant improvement was obtained.

How were the studies combined?

The studies were described in the text and tables and combined in a narrative.

How were differences between studies investigated?

Differences between the studies were discussed in the text or were apparent from the tables.

Four comparative studies (n=235) were included: one RCT (n=116) and three non-randomised prospective comparative studies (n=119).

The RCT (116 patients in primary care who requested ear syringing) reported that hearing in patients who underwent ear irrigation was clinically significantly improved (defined as an improvement in hearing of 10 dB or more) in 33% of patients; the mean improvement was 24 dB (95% CI: 11.6, 37.4) and the NNT was 3.1. The primary study authors reported that 'very few' patients reported adverse events, but presented no data. The RCT adjusted for single and bilateral ear impaction and the hearing was measured by an assessor blinded to the treatment group.

One study (19 new admissions from acute care to residential care; 27 ears tested at 20, 25 and 40 dB) reported that 80% of the ears tested heard new frequencies after ear irrigation; results for the individuals were not reported. The study did not control for background noise and the audioscope operator was not blinded to the treatment group.

Another study (79 patients admitted to non-intensive care units; 124 ears tested with audioscope at 40 dB) reported that 75% of the ears tested heard 1 to 3 more frequencies after ear irrigation (mean 1.54, SD 0.6). One patient heard one frequency less after syringing. The study did not report whether the audiologist was blinded or whether background noise was controlled for.

A third study (21 patients with moderate to severe high-frequency sensorineural hearing loss attending an ear, nose and throat out-patient clinic) reported that the mean increase in hearing threshold after ear irrigation was 5.45 dB (95% CI: 0.59, 20.47), measured by pure tone audiometry. The study did not report whether the audiologist was blinded.

The results from one RCT suggested that hearing may improve significantly after ear irrigation in a minority of patients. However, the results of the RCT might have been overestimated and more evidence is required.

This single-author review addressed a clear question that was defined in terms of the participants, intervention, outcomes and study design. Several relevant sources were searched but no attempts to minimise publication or language bias were reported; in addition, the dates searched were not reported. The methods used to select studies and extract the data were not described in full, but the single-authorship suggested that they might not have been performed in duplicate, which could have led to reviewer errors and bias.

A formal validity assessment was not reported, but relevant aspects of study quality were considered in the text. It should be noted that although all included studies had a control group, no data for the control groups, or comparisons between treatment and control groups, were presented. In view of the small number of diverse included studies, a narrative synthesis that took account of study quality was appropriate. The review methods were poorly reported and the potential for bias in the review should not be ignored. However, the author's cautious conclusions appear to reflect the limitations of the evidence presented.

Practice: The author did not state any implications for practice.

Research: The author stated that more research to evaluate the effects of ear irrigation on hearing and adverse events is required.

This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn.