Carpal Tunnel Syndrome in Patients on Intermittent Hemodialyis

less than 60.3 months. By comparison, other authors reported the prevalence of CTS as 0 at 5 years [2] when low-flux membranes and commercial (potentially contaminated) dialysis fluid were used. Busch et al. [1] clearly overestimated the prevalence of CTS in their patients (median follow-up 31 months). (2) Cross-sectional studies may establish associations, but not causality. Due to the nonrandomized design, confounders may be unequally distributed among subgroups. Indeed, in the study by Busch et al. [1] , patients treated with high-flux biocompatible dialyzer membranes had the highest dialysis duration, the lowest residual diuresis, and the highest circulating  2 -microglobulin concentrations. Moreover, the use of high-flux membranes was associated with a higher prevalence of CTS in the multivariate logistic regression analysis. These data are in contrast to other reports demonstrating lower  2 -microglobulin levels in high-flux HD compared to low-flux HD of similar HD vintage and a lower prevalence of CTS in these patients [3, 4] . Busch et al. [1] report a high prevalence of carpal tunnel syndrome (CTS) in hemodialysis (HD) patients in spite of the use of high-flux dialyzer membranes and ultrapure dialysis fluid. The article is of interest as dialysis-related amyloidosis (DRA) has been out of focus in the last decade. The interpretation of the data presented is, however, hampered by the disadvantages of the cross-sectional study design they chose. (1) One major pitfall of this descriptive study is the absence of a clear, specific and reproducible disease definition. The gold standard for the diagnosis of DRA manifestations remains the immunohistological detection of amyloid. Clinical assessment of symptoms and signs may pave the way to the diagnosis, but do not prove the presence of amyloid deposits in CTS. The authors do not differentiate between different causes (diabetes) of CTS nor grade the severity of destructive arthropathy, which may lead to overdiagnosis. The authors found a prevalence of CTS of 28.7% in HD patients with a dialysis vintage of Published online: January 9, 2013