Validation of occupational hand use categories.

As part of a study of the etiology of carpal tunnel syndrome in industry, we developed a measure of occupational hand use activities, "Occupational Hand Use" (OHU), using 471 workers from four industries. This categorization has five categories based primarily upon observed relative force and secondarily upon observed relative repetitions. Because the validity of this OHU categorization has been questioned, we devised a study to validate this variable by demonstrating its reliability. Using discriminant analysis, we show that the OHU categorization accurately reflects the subjective impressions of other industrial workers (605 workers from four other industries in the United States and Japan). Within each validation industry, 68 to 88% of all workers were classified precisely to the correct OHU category, and an additional 10 to 25% were classified to within one OHU category, for a hit or near-miss rate of 87 to 98%. The major classification error was due to some workers overestimating the repetitiousness of their jobs. An equation for calculating OHU from subjective or objective data is provided.