The clinical effectiveness of olive oil administered as drops or spray before microsuction to remove occluding ear wax in adults: a cluster randomised control trial

Earwax is a natural substance that protects and lubricates the ear canal. Excessive earwax can occlude the ear canal and cause hearing loss, tinnitus and discomfort. With around 2.3 million UK patients requiring earwax removal each year, it is one of the commonest procedures performed in primary care. Practice guidelines currently recommend the use of pretreatment softeners to aid subsequent removal of earwax by suction or irrigation. One commonly used pretreatment softener is olive oil, which can be administered as drops or spray. The spray is more expensive than drops, but there are anecdotal reports that it is easier to administer than drops; however, its comparative effectiveness to drops is unknown. The preregistered cluster randomised control trial (RCT) reported in this thesis addressed this gap in knowledge.

Part one of the thesis includes an introduction to the topic (Chapter 1) along with a summary of the literature (Chapter 2). There are at least three reviews published on the management of earwax. Since few new studies on the topic have been published, the decision was taken not to conduct a new systematic review as part of this thesis.

Part two, the main body of the thesis, reports the research study that compared the clinical effectiveness of olive oil administration methods. The research question, written in PICOS format, was, “In adults with excessive earwax (Participants), does pretreatment olive oil spray (Intervention) increase successful removal of the earwax at first attempt (Outcome) compared to olive oil drops (Control) when conducted in primary care (Setting). Secondary outcomes included comparing the improvements in self-reported symptoms post-microsuction, the amount of residual wax post-microsuction and the number of adverse events. The study was designed in partnership with a panel of patient and public involvement (PPI) volunteers. The contribution from the PPI volunteers shaped the study design e.g. acceptability of methodology and content of patient information material. A cluster RCT design was used with 26 GP practices randomised 1:1 to each arm. With an expected 67 participants in each cluster i.e., 871 in each arm, the study was powered to show a difference in primary outcome between the two arms of 9%. Chapter 3 is the research protocol, submitted to Trials journal, written following Standard Protocol Items: Recommendations for Interventional Trials (SPRINT) guidance. Since preregistration promotes research integrity and improves transparency by reducing reporting bias, the study was preregistered on two registers – Open Science Framework (OSF: https://doi.org/10.17605/OSF.IO/9C7F8) and International Standard Registered Clinical/Social Study Number (ISRCTN: https://www.isrctn.com/ISRCTN28211073?q=earwax&filters=&sort=&offset=1&totalResults=3&page=1&pageSize=10).

All 26 clusters completed the trial but the targeted number of participants per cluster was not achieved in 16 clusters. This means the statistical power to detect a mean difference between arms of 9% was reduced to 74.3%. In addition, adherence to the intervention was 38%. Successful earwax removal at the first attempt was achieved in 86% and 81% in the intervention and control arm, respectively. The difference between arms was not statistically significant. The results show that hearing difficulty was the most common symptom (50.6%) prior to earwax removal. Symptoms were reported as much or somewhat better in 80% and 87% of cases in the intervention and control arm, respectively. This difference was statistically significant and probably reflects the lower success of earwax removal in the intervention arm. Incomplete earwax removal was 15.8% and 13.1% in the intervention and control arm, respectively. This difference was not statistically significant. Four patients reported adverse events during the data collection period, one in the intervention arm and three in the control arm. Overall, there was no evidence to suggest that administration of olive oil as a spray (intervention) is clinically more effective than olive oil drops (control). However, this conclusion should be treated with caution, given the study was underpowered and adherence was low. The RCT is presented in Chapter 4, prepared as a submission-ready draft for the British Journal of General Practice.

The thesis concludes in part three (Chapter 5) with a critical appraisal of the research. The appraisal includes a discussion of the study’s overall strengths and weaknesses and concludes with a personal reflection of conducting research as part of the Higher Specialist Scientist Training (HSST) programme.

Outputs

British Academy of Audiology magazine article – My HSST research approvals journey – Autumn 2024

Association of Health Care Science Leadership journal article – Breaking Ground: Reflections on getting research – Summer 2025 https://www.ahcs.ac.uk/wp-content/uploads/2025/06/LHCS-magazine_Summer_2025_v12.pdf

Pre-registration: OSF: https://doi.org/10.17605/OSF.IO/9C7F8 and International Standard Registered Clinical/Social Study Number ISRCTN: https://www.isrctn.com/ISRCTN28211073?q=earwax&filters=&sort=&offset=1&totalResults=3&page=1&pageSize=10

Pre-registered research protocol paper submission to Trials journal – accepted for publication subject to minor revisions, available as pre-print: https://doi.org/10.21203/rs.3.rs-6394074/v1

Study manuscript titled “Clinical effectiveness of pretreatment drops or spray for wax removal: Cluster randomised trial” in preparation for submission to British Journal of General Practice journal.