Temperature Effects on Vibrotactile Sensitivity Threshold Measurements: Implications for Carpal Tunnel Screening Tests Edward Klinenberg, PhD, BrooksAFB, TX, Yuen So, MD, PhD, David Rempel, MD, San Francisco,CA This study examines the effect of skin temperature on fingertip vibrotactile sensitivity mea- surements and the resulting implications for carpal tunnel syndrome screening tests. Twenty subjects (11 men, 9 women) were tested for fingertip vibrotactile thresholds using the method of limits at four different frequencies (31.5, 125, 250, and 500 Hz) and six temperature cate- gories (17~176 20~176 23~176 26~176 29~176 32~176 Vibrotactile sensitiv- ity thresholds increased with decreasing fingertip skin temperature. Furthermore, the relation- ship was a function of vibration frequency. Higher frequencies were more affected by temperature than lower frequencies, with significant effects beginning at 29~ These temper- ature-related effects may lead to possible false positive results in screening for carpal tunnel syndrome or other neuropathies. To minimize potential temperature-induced misclassification errors during these screening tests, fingertip skin temperature should be recorded before mea- surement and probably maintained above 29~ during the measurement. (J Hand Surg 1996;21A:132-137.) Multifrequency vibrometry has been proposed as a screening tool for the early detection of carpal tunnel syndrome (CTS). 1.2 Using a multifrequency vibrome- ter, the vibrotactile sensitivity at a subject's fingertip can be measured at a variety of frequencies during a single test. Lundborg et al. 2 proposed measuring From the Ergonomics Branch, Occupational and Environmental Health Directorate, Armstrong Laboratory, Brooks Air Force Base, TX, and the Department of Neurology and Ergonomics Program, University of California, San Francisco, San Francisco, CA. This study was supported, in part, by USAF Clinical Investigations Protocol 92-110. This paper is declared a work of the United States gov- ernment and is r~ot subjected to copyright protection in the United States. Received for publication Jan. 13, 1995; accepted in revised form June 26, 1995. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: David Rempel, MD, Ergonomics Program, University of California, San Francisco, 1301 South 46th Street, Building 112, Richmond, CA 94804. 132 The Journal of Hand Surgery vibrotactile sensitivities over a series of octave band frequencies from 8 to 500 Hz (ie, 8, 16, 31.5, 63, 125, 250, 500 Hz) for CTS screening and diagnosis. According to Lundborg et al., 2 the earliest signs of CTS development occur in the higher measured fre- quencies (> 125 Hz). By comparing the absolute value and shape of the seven individual frequencies 3 or a composite index derived from the seven individual fre- quencies ~ to a normal population, it is hypothesized that individual CTS status can be successfully classi- fied. Neese and Konz 4 have suggested that only the top three frequencies (125,250, 500 Hz) and perhaps only the top two frequencies (250 and 500 Hz) may be needed for the early detection of CTS. Other studies using single-frequency (120 Hz) 5'6 and multiple- frequency (50, 150 Hz) 7 vibrometers have been con- ducted with mixed results for the early detection of CTS. Many factors may influence vibrotactile sensitivity measurements. These include contact force, effect of surround, 8 contactor area, 9 age and height, ~~ and skin