Intertester reliability of manual muscle strength testing in leprosy patients

This study reports the results of a study on the intertester reliability of manual muscle strength testing in leprosy patients with confirmed motor function loss of at least one nerve. Three testers graded the muscle strength of 72 patients in random order. Both hands and feet were graded. Strength was graded on a modified Medical Research Council Scale (9 points, 5, 4+, 4, 3+, 3, 2+, 2, 1, 0). The following movements were tested for strength: little finger and index finger abduction, intrinsic position of all four fingers, thumb abduction and opposition, foot dorsiflexion and eversion and extension of the big toe. The weighted kappa statistic was used to calculate the chance-corrected percentage of agreement between observers. Overall agreement for each of the 11 tests appeared to be good or very good (0.61-1.00). However, when data for hands or feet with normal strength or complete paralysis were excluded from the analysis, the reliability of the remaining mid-range scale was not acceptable (kappa 0.55-0.88, direct agreement range 11-41%). While the reliability of this scale could possibly be improved by special training, we feel that, for the evaluation of nerve function for leprosy patients with (suspected) nerve function loss, the extended 9-point VMT scale should only be used when direct intra- or intertester agreement is more than 80%.