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. 2017 Nov 28;1(25):2414-2420.
doi: 10.1182/bloodadvances.2017010942.

Misdiagnosis of primary immune thrombocytopenia and frequency of bleeding: lessons from the McMaster ITP Registry

Donald M Arnold  1   2   3 , Ishac Nazy  1   2 , Rumi Clare  1 , Anushka M Jaffer  1   2 , Brandon Aubie  1   2 , Na Li  1   2 , John G Kelton  1   2
Affiliations

Misdiagnosis of primary immune thrombocytopenia and frequency of bleeding: lessons from the McMaster ITP Registry

Donald M Arnold et al. Blood Adv. .

Abstract

Nonspecific diagnostic criteria and uncertain estimates of severe bleeding events are fundamental gaps in knowledge of primary immune thrombocytopenia (ITP). To address these issues, we created the McMaster ITP Registry. In this report, we describe the methodology of the registry, the process for arriving at the diagnosis, and the frequency of bleeding. Consecutive patients with platelets <150 × 109/L from a tertiary hematology clinic in Canada were eligible. Patients completed a panel of investigations and were managed per clinical need. Two hematologists initially determined the cause of the thrombocytopenia using standard criteria and reevaluated the diagnosis over time, which was adjudicated at regular team meetings. Bleeding was graded from 0 (none) to 2 (severe) prospectively using an ITP-specific tool. Data were validated by duplicate chart review and source verification. Between 2010 and 2016, 614 patients were enrolled. Median follow-up for patients with >1 visit was 1.7 years (interquartile range, 0.8-3.4). At registration, 295 patients were initially diagnosed with primary ITP; of those, 36 (12.2%) were reclassified as having a different diagnosis during follow-up. At registration, 319 patients were initially diagnosed with another thrombocytopenic condition; of those, 10 (3.1%) were ultimately reclassified as having primary ITP. Of 269 patients with a final diagnosis of primary ITP, 56.5% (95% confidence interval [CI], 50.4-62.5] experienced grade 2 bleeding at 1 or more anatomical site, and 2.2% (95% CI, 0.8-4.8) had intracranial hemorrhage. Nearly 1 in 7 patients with primary ITP were misdiagnosed. Grade 2 bleeding was common. Registry data can help improve the clinical and laboratory classification of patients with ITP.

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Conflict of interest statement

Conflict-of-interest disclosure: D.M.A. has been a consultant for Amgen, Novartis, BMS, Rigel, and UCB on new and established ITP medications and received research funding for ITP studies from Amgen and Novartis. The remaining authors declare no competing financial interests.

Figures

None
Graphical abstract
Figure 1.
Figure 1.
Worst bleed ever by anatomical site among patients with primary ITP. Of 269 patients, 152 (56.5%) experienced 1 or more grade 2 bleed; 25 (16.4%) had skin bleeding only.
See this image and copyright information in PMC

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