Prevalence of clinical referrals having hearing thresholds within normal limits.

Objectives: To document the prevalence of clinically normal air conduction thresholds (0.5-4 kHz, bilaterally, ≤20 dB HL) among children and adults in a large audiology service and to estimate the prevalence of auditory processing disorder (APD).

Design: Over a period of one year, clinicians implemented their usual protocol and recorded a brief history for those with normal audiometry.

Study Sample: The number of people seen by the service was 2924 children (0-16 years old) and 4757 adults (17-100 years old).

Results: Adults and school-age children were most commonly referred by their primary care doctor for difficulties listening in noise or following a conversation, and younger children by their home health visitor for speech production problems. Children tended to be referred on to speech pathology or APD clinics whereas adults were discharged.

Conclusions: The prevalence of normal cases was 5.1% among the children and 0.9% among all adults. For younger adults (17-60 years, n = 1025), the prevalence was 4.0%. Based on comparison with those referred with hearing loss, we estimate the prevalence of APD among children and adults, defined as listening problems despite normal audiometry, to be about 0.5-1.0% of the general population.