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

Vollständiger Abstract

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Purpose: 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. Method: 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. Results: 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. Conclusions: 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.