SCREENING FOR CARPAL-TUNNEL SYNDROME IN THE WORKPLACE - AN ANALYSIS OF PORTABLE NERVE-CONDUCTION DEVICES

Several devices have been developed for rapid motor or sensory median nerve conduction testing. We evaluated the validity, and reliability o f the Neurosentinel(R) (NS) and NervePace(R) (NP) electroneurometer fo r sensory and motor testing; respectively, compared with formal electr odiagnostic studies (EDS), and examined their potential role in workpl ace screening for carpal tunnel syndrome (CTS). Thirty-two working sub jects without CTS were examined and tested with the NS, NP, and EDS, a nd retested one week later. Subjects were selected who did not have CT S, other hand or nerve problems, or jobs with significant ergonomic ri sks, in order to decrease the likelihood of changes over time in media n nerve function. Mean co?relations of NP and NS with EDS latencies ra nged from r = 0.69 to r = 0.85, with somewhat better correlation for N S (sensory) than NP (motor). Test-retest reliability was greatest for motor EDS (r = 0.86 to 0.91) and similar for sensory EDS, NS, and NP ( r = 0.72 to 0.79); mean results were very similar Based on the observe d relationship between NS or NP and EDS results, confidence intervals were calculated to represent the range of EDS results consistent with a single NS or NP measurement. These intervals ranged from +/- 0.3 mil liseconds (ms) for NS to +/- 0.6 msec for NP, with similar ranges for change over time in an individual. The magnitude of these intervals fo r a single test or individual implies that the NS and NP are unlikely to identify individuals with CTS or to detect changes over time that a re not accompanied by symptoms or signs. The screening devices are not likely to be useful in confirming early CTS, when single latency valu es may be normal, and detailed EDS may be necessary to detect nerve en trapment. Compared with EDS, these devices have moderate validity and similar reliability; they are probably most useful for cross-sectional or longitudinal studies of groups, but care must be taken in using th em for pre-placement or surveillance tests of individual workers. Fals e-positive results may lead to discrimination, inappropriate referrals and interventions; false-negative tests can result in inappropriate r eassurance and missed opportunities for intervention.