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Assessment of a modified 4T scoring system for heparin-induced thrombocytopenia in critically ill patients.

[heparin-induced thrombocytopenia]

The purpose of the study is to determine if a modified 4T (m4T) scoring system, which omits clinical evaluation of other thrombocytopenic etiologies, is different from the 4T scoring system's probability to predict a positive heparin-induced thrombocytopenia (HIT) laboratory test in the intensive care unit.This is a single-centered retrospective analysis of critically ill adults who had an enzyme-linked immunosorbent assay antiplatelet factor 4 antibody (ELISA anti-PF4 Ab) ordered. Patients were identified as HIT positive (optical density, 0.40) or HIT negative (optical density, <0.40) based on the ELISA anti-PF4 Ab. Both 4T and m4T scores were calculated, and the diagnostic accuracy was compared using paired receiver operating characteristic curves.A total of 1487 adult intensive care unit patients with an ELISA anti-PF4 Ab ordered between January 2007 and December 2009 were eligible for study enrollment. Application of exclusion criteria and random selection yielded a total of 232 patients included for analysis (58 HIT-positive and 174 HIT-negative patients). The area under the curve for the 4T and m4T scores were 0.683 (95% confidence interval, 0.604-0.762) and 0.680 (95% confidence interval, 0.600-0.759), respectively (P=.065).This study does not show a difference in the probability of the m4T and 4T scoring systems to predict a positive ELISA anti-PF4 Ab test in the critically ill patient population. Further prospective studies are needed to validate the m4T scoring system.