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First ‘core outcome set’ for ear infection studies in primary and community care

GP uses a medical instrument to see inside a young child's ear.

7 May 2025

Researchers have produced a standard set of outcomes that should be measured and reported in future studies involving common acute ear infections. This ‘core outcome set’ will allow future ear infection studies to be more consistent with each other, so evidence can be accumulated over time.

The work, involving researchers from the Centre for Academic Primary Care, University of Bristol and NIHR Applied Research Collaboration (NIHR ARC) West, is published in BMC primary care.

‘Acute otitis media’ – an infection in the middle ear – is very common. About 80 per cent of children will have an ear infection at least once.

The infection causes pain and distress to the child and parents, frequently results in health service consultations and is the most common infection for which a child is given antibiotics worldwide.

Studies of treatments for ear infections are important, to explore alternatives to prescribing antibiotics. Inappropriate use of antibiotics is one of the key drivers of antibiotic resistance and is a global health priority.

There have been many studies of ear infection treatments, but these have varied widely in their design, the types of treatment, populations studied, and outcome measures. This makes drawing overarching conclusions difficult.

In this study, researchers worked with parents, GPs, Traditional Complementary and Integrative Medicine professionals and pharmacists to identify a core outcome set for middle ear infection studies in primary and community care. An International Steering Committee then discussed and agreed the final core outcome set.

They identified ten core outcomes: eight acute outcomes and two mid to long term outcomes.

Acute outcomes:

  • Severity of symptoms, for example fever, irritability, unusual crying or screaming, lack of drive, loss of appetite and unusual sleep behaviour
  • Pain severity
  • Pain duration
  • Symptom duration
  • Fever above 38oC
  • Painkiller use
  • Antibiotic use
  • Adverse events and serious complications

Mid to long term outcomes:

  • Recurrence or number of recurrences in the next 12 months
  • Fluid leaking from the ear

This defines a minimum set of outcomes to be measured and reported in future primary care and community studies of acute middle ear infections.

Dr Esther van der Werf, Honorary Senior Lecturer, Centre for Academic Primary Care, University of Bristol and lead author, said: "Our new core outcome set is a landmark contribution to integrative and conventional medicine by addressing a long-standing barrier in clinical research for acute otitis media, that of outcome inconsistency. The outcomes reflect not just clinical priorities but also what matters most to patients, ensuring that patient-centred care is at the heart of future research."

Rachel Perry, Research Fellow at the University of Bristol and NIHR ARC West said: “This is the first core outcome set for acute otitis media to be used for primary and community care studies. Implementing it in future studies will help to make the best use of limited research resources, by facilitating comparison and synthesis of results across studies.”

Paper: A core outcome set for acute otitis media (COS-AOM) for primary and community care studies by Esther T. van der Werf et al. Published in BMC Primary Care. April 2025.

Further information

About the Centre for Academic Primary Care, University of Bristol

The Centre for Academic Primary Care (CAPC) at the University of Bristol is a leading centre for primary care research in the UK, one of nine forming the NIHR School for Primary Care Research. It sits within Bristol Medical School, an internationally recognised centre of excellence for population health research and teaching. Follow on Bluesky: @capcbristol.bsky.social and LinkedIn.

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