Carpal tunnel syndrome diagnosis in occupational epidemiological studies

The problem of the possible overdiagnosis of carpal tunnel syndrome (CTS) has been raised in the Occup Environ Med.1–3 CTS, like almost all medical conditions, occurs along a spectrum of presentation, progression and severity and, therefore, the alignment between symptoms, signs and objective tests is imperfect. A finding often misunderstood and reported in general population and workplace studies, is the dissociation between CTS symptoms and median nerve conduction slowing at the wrist.4–7 CTS symptoms and nerve conduction slowing have two different mechanisms, nerve sensory fibres autonomous discharge and conduction block (and or slowing) of the fastest nerve ibres. The two phenomena are likely due to the same causal factor, for example, compression of the median nerve in the carpal tunnel, but the processes are different, so it should not be surprising that in some individuals the onset of these changes do not occur at the same time. Furthermore, there are no internationally accepted standards for abnormal median nerve conduction at the wrist; thresholds between laboratories vary, and this variability and differences in test methods can have an impact on case classification.