Sensitivity and specificity of nerve palpation, monofilament testing and voluntary muscle testing in detecting peripheral nerve abnormality, using nerve conduction studies as gold standard; a study in 357 patients.

OBJECTIVE: To determine sensitivity and specificity of clinical tools viz. nerve palpation (NP), monofilament (MF), and voluntary muscle testing (VMT), for assessing peripheral nerve function impairment (NFI) in leprosy, using nerve conduction studies (NCS) as gold standard.

STUDY POPULATION AND METHODS: 357 untreated multibacillary (MB) leprosy patients were assessed using above tests. The nerves assessed were left and right ulnar, median, radial cutaneous, sural, common peroneal and posterior tibial. The concordance between the clinical and NCS tests was done for each nerve. The sensitivity and specificity of clinical tests for detecting nerve impairment was determined, using NCS as gold standard. Analysis was performed using SPSS version 10.0.

RESULTS: The sensitivity of NP ranged between 71% to 88% for all nerves, except the median (43%) and sural (59%) nerves. Specificity was > 60% for all, but low for ulnar (34%) and common peroneal (40%) nerves. The specificity of MF testing was > 80% and of VMT assessment was >90% for all nerves. The sensitivity of MF testing ranged between 35-44%, while of VMT assessment was very low i.e. 4-5%, the maximum was for the ulnar nerve (25%). Detection sensitivity of MF testing and VMT assessment improved two fold when combined with NP and was closely comparable to NCS test findings.

CONCLUSIONS: Both MF testing and VMT assessment showed good specificity, but moderate to low sensitivity. NP was less specific but more sensitive than MF testing and VMT assessment. Combining NP with MF testing and VMT assessment gives a two fold improvement in the sensitivity for assessing nerve damage and could therefore serve as the most useful clinical tools for diagnosis of leprosy and detecting nerve damage at field level.