Best Initial Test for Conductive Hearing Loss
Pure-tone audiometry (PTA) with both air and bone conduction testing is the gold standard and definitive test for diagnosing conductive hearing loss, as it directly measures the air-bone gap that defines this condition. 1
Initial Clinical Assessment
When audiometry is not immediately available, tuning fork tests (Weber and Rinne) combined with otoscopic examination serve as the best bedside screening tools to preliminarily distinguish conductive from sensorineural hearing loss before formal testing. 1
Proper Tuning Fork Technique
Weber Test:
- Strike a 256 or 512 Hz tuning fork on your covered elbow or knee (never on hard surfaces, which create nonharmonic frequencies) 1, 2, 3
- Place the vibrating fork at midline of forehead or on maxillary teeth 1, 2
- Ask where the sound is heard 1, 2
- In conductive hearing loss, sound lateralizes to the affected ear 1, 2
Rinne Test:
- Strike the same tuning fork properly 1, 3
- Place over mastoid bone, then move to ear canal entrance 1, 2
- In conductive hearing loss, bone conduction is heard better than air conduction (negative Rinne) 1, 2
- Normal ears hear air conduction louder than bone conduction 1, 2
The 256 Hz fork is superior to 512 Hz for detecting conductive losses, correctly identifying 87% of cases with a 25 dB air-bone gap and 95% with a 30 dB gap, with specificity exceeding 90%. 4
Alternative When Tuning Fork Unavailable
The "hum test" can substitute for Weber testing with similar diagnostic accuracy—ask the patient to hum, and if they hear their own hum louder in the affected ear, conductive hearing loss is likely in that ear. 1, 3
Definitive Diagnostic Testing
Comprehensive audiometric evaluation must include: 1
- Pure-tone air conduction thresholds
- Pure-tone bone conduction thresholds
- Speech audiometry
- Tympanometry
- Acoustic reflex testing
The air-bone gap on PTA definitively establishes conductive hearing loss—an air-bone gap ≥15-20 dB at frequencies 0.5,1,2, and 4 kHz confirms the diagnosis. 1, 5, 6 PTA is considered low-risk, low-cost, and can be repeated to monitor changes over time. 1
Imaging When Indicated
After confirming conductive hearing loss on audiometry, CT temporal bone without contrast is the first-line imaging modality when no middle ear mass is visible on otoscopy. 1 CT excellently delineates:
- Ossicular chain abnormalities (erosion, fusion, fixation) 1
- Otosclerosis/otospongiosis 1
- Superior semicircular canal dehiscence 1
- Round window occlusion 1
MRI has no role in initial conductive hearing loss evaluation, as it cannot adequately visualize bony structures. 1
Critical Pitfalls to Avoid
- Never assume conductive hearing loss without audiometric confirmation—misdiagnosing sensorineural hearing loss as conductive can delay critical treatment for conditions like sudden sensorineural hearing loss. 1
- Remove impacted cerumen before establishing the diagnosis, as it causes conductive hearing loss that confounds assessment. 2, 7
- Tuning fork tests do not replace formal audiometry—they provide preliminary information only. 1
- Ensure testing occurs in a quiet environment to minimize ambient noise interference. 2
Screening Tests Performance
Simple screening methods have reasonable accuracy compared to PTA: whispered voice test, single-question screening ("Do you have difficulty with your hearing?"), and handheld audiometers all show positive likelihood ratios of 3.0-5.8 and can identify patients needing formal evaluation. 1 However, these are screening tools only and cannot diagnose conductive hearing loss definitively. 1