Donald M. Arnold, MD, MSc; Mark A. Crowther, MD, MSc
Potential Financial Conflicts of Interest: Dr. Arnold has received a grant from Hoffman-LaRoche, Canada, for the conduct of a clinical trial of rituximab in ITP.
Arnold DM, Crowther MA. Rituximab for Patients with Idiopathic Thrombocytopenic Purpura. Ann Intern Med. 2007;147:281-282. doi: 10.7326/0003-4819-147-4-200708210-00019
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Published: Ann Intern Med. 2007;147(4):281-282.
We appreciate the comments from Drs. Peñalver and Cabrera about our systematic review of rituximab in ITP. Our inclusion criteria for primary reports in the review had to be fairly liberal because most reports were case series or cohort studies, reflecting, perhaps surprisingly, the paucity of methodologically rigorous trials in this field. Nevertheless, we established a priori that care must be taken to avoid redundant publications, because many were published in abstract form only and some were follow-up reports of preliminary studies.
The report by Peñalver and colleagues gave us reason to pause (1). In fact, the authors were kind enough to share their raw data with us for further contemplation. True, their report of 89 patients with ITP treated with rituximab was the largest of any published series, and indeed, patient follow-up was complete. However, their report described the results of a questionnaire sent to 43 different centers in Spain. Our principal reservation about the paper was that we could not be sure that the data contributed by the patients had not been reported elsewhere (that is, their originality). Moreover, survey data are particularly prone to recall and reporting bias, and measures to safeguard against these methodological pitfalls were not described in the paper. As Drs. Peñalver and Cabrera surmise, the inclusion of their report in our systematic review does not significantly change the estimated overall response to rituxumab (62.0% vs. 62.5%), but it does tighten somewhat the 95% CIs (53.0% to 71.0% vs. 52.6% to 72.5%).
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