Clinical Prevalence and Impact of False Air-Bone Gaps in Clinical Audiometry: A Study of 1,000 Ears

Accurate hearing loss classification depends on air-bone relationships; however, "false" air-bone gaps (ABGs) in sensorineural hearing loss (SNHL) frequently compromise diagnostic clarity. By shifting the focus from ABG magnitude to clinical prevalence, this study uses the prevalence of clinical ABGs (≥ 15 dB) as a primary metric to quantify diagnostic ambiguity in routine practice and to evaluate the efficacy of bone-conduction (BC) testing at frequencies where frequent false ABGs occur.

We retrospectively analyzed audiometric data from 1,000 ears (500 adults). The analysis focused on the prevalence of clinical ABGs and ABG magnitudes across the tested frequencies, including a secondary analysis of their relationship with hearing loss severity. The clinical utility of the 250-Hz BC threshold was evaluated by examining whether audiologists relied on an isolated 250-Hz ABG when classifying hearing loss as conductive or mixed.

False ABGs in SNHL were most common at 250 Hz (43.5%) and 4000 Hz (13.9%), with an increasing severity of hearing loss. Audiologists did not rely on isolated ABG at 250 Hz to classify hearing loss as conductive, as all confirmed conductive/mixed cases were detected by ABGs at other frequencies. At 4000 Hz, false ABGs were intensity-dependent artifacts, mainly appearing when the air-conduction thresholds were 50 dB HL.

False ABGs often occur at 250 and 4000 Hz. Routine 250-Hz BC testing is unnecessary for most adults and lacks diagnostic value. Focusing on the 500- to 4000-Hz range and using the cross-check principle for 4000-Hz high-intensity thresholds will improve accuracy and efficiency.