Background: Determination of auditory function is a fundamental part of a complete neurologic examination. Disability from permanent hearing loss is common in the general population. Current bedside auditory tests are unreliable and cumbersome. We evaluated the calibrated finger rub auditory screening test (CALFRAST) as a routine diagnostic tool.
Methods: The sound spectrum and mean peak intensities of standard finger rub were measured, as well as background noise. CALFRAST overlapped the frequency spectrum of normal speech. Patients and companions were recruited from a neurology clinic. With arms extended, two stimulus intensities were presented: strong finger rub (CALFRAST-Strong 70) and the faintest rub that the examiner could hear (CALFRAST-Faint 70). With subjects' eyes closed, each ear's CALFRAST threshold was ascertained and then compared with its audiometric measure. The normal threshold was considered to be 25 dB. Validity, reliability, and discrimination abilities were obtained using standard methods.
Results: Two hundred twenty-one subjects (442 ears; 58% women) were examined. Ages ranged from 18 to 88 years, with a mean of 46 years. Eighty-five subjects (39%) had some degree of hearing loss. Both specificity and positive predictive value of CALFRAST-Strong 70 were 100%. Both sensitivity and negative predictive value of CALFRAST-Faint 70 were 99%, with a negative likelihood ratio <0.1. Area under the receiver operating characteristic curve was 0.94, consistent with excellent discrimination ability. Both intrarater and interrater reliability were excellent, both kappa >0.8. Subjects' self-assessment of hearing was unreliable.
Conclusion: The calibrated finger rub auditory screening test (CALFRAST) is simple, accurate, inexpensive, and reliable. As a routine screening tool, CALFRAST may contribute to more efficient identification of auditory impairment.