Case reports and studies on pityriasis rosea – from number of patients to meta-analyses and diagnostic criteria

摘要

We read with admiration the case report by Brzezinski and Sinjab on pityriasis rosea (PR) in a 12-month-old infant [1]. Despite more than a century of research, the underlying viral aetiologies, immunopathogenesis, diagnostic methods, specific diagnostic investigations, and optimal evidence-based management of PR are not yet within reach. There exist many case reports which, like the present report, are outstanding in supplementing individual clinical data to original studies on PR.However, original studies in PR [2-4] were typically performed on a relatively small number of patients, say below 100 patients. Owing to these small numbers, the powers of individual studies are low. Theoretically, these studies can be meta-analysed to achieve high statistical powers and high clinical significance. However, a Cochrane review [5] has pointed out that such meta-analyses cannot be validly performed as the diagnosis of PR is clinical and various investigators adopt different inclusion and exclusion criteria in their studies. The high heterogeneity between study populations limits not only meta-analyses but also systematic reviews. We have previously reported a study on 1379 patients with PR [6]. However, we admit that as our data was from three geographical locations with differing diagnostic criteria, the heterogeneity of these patients was high