Risk of herpes zoster in SLE Chen HH et al. administrative data reported by physicians, may be a concern. Although the Bureau of National Health Insurance routinely samples patient charts to randomly cross-check the claims from all of the hospitals, a bias due to miscoding and misclassification may occur. Second, the lack of information about self-treatment with over-the-counter medications in the NHIRD may lead to underestimation of HZ. Third, an information bias may arise if the SLE patients have a greater tendency to visit physicians instead of using self-treatment with over-the-counter medications for cutaneous problems than the non-SLE patients. Another information bias may occur if physicians are more alert to the diagnosis of HZ in patients with SLE than in patients without SLE. Lastly, the administrative database cannot offer information about the SLE disease severity, which may also be a confounding factor for the results of the present study. 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