Concurrent medical disease in work-related carpal tunnel syndrome.

BACKGROUND Work-related carpal tunnel syndrome (CTS) now accounts for more than 41% of all repetitive motion disorders in the United States. Carpal tunnel syndrome is also associated with obesity and many different medical diseases. PATIENTS AND METHODS Two hundred ninety-seven patients medically certified with a work-related upper extremity industrial illness underwent a systematic search for concurrent medical diseases. Diagnoses of CTS were made using 4 separate case definitions. RESULTS One hundred nine separate atraumatic illnesses (mainly hypothyroidism, diabetes mellitus, and various arthropathies) capable of causing arm pain or CTS were diagnosed in a third of all patients. Using record reviews and patient histories alone, 68% of these conditions would have been missed. One hundred ninety-eight patients had been diagnosed as having CTS 420 times in more than 1000 office visits, but diagnostic laboratory studies were ordered only 25 times. Every case definition of CTS was significantly associated with a related medical condition. Two definitions yielded more than 41% prevalence of concurrent disease (odds ratio, > or = 2.36; P < or = .004), and up to two thirds of these patients had either a medical disease or were obese (odds ratio, > or = 3.15; P < or = .001). Two cohorts totaling 114 patients (38%) working for companies employing nearly 19,000 people included all CTS claims filed during 2 evaluation periods. They did not differ from the other patients with CTS with respect to age, concurrent disease, or obesity. CONCLUSIONS Routine patient histories and record reviews are inadequate for proper evaluation of work-related CTS. Unrecognized medical diseases capable of causing CTS are common. Studies asserting an association between occupational hand usage and CTS are of questionable validity unless they prospectively account for confounding disease and obesity.