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Clinical and laboratory characteristics associated with a high optical density anti-platelet factor 4 ELISA test

Authors Lu B, Kudlowitz D, Gardner L

Received 9 June 2015

Accepted for publication 26 August 2015

Published 19 November 2015 Volume 2015:6 Pages 277—283


Checked for plagiarism Yes

Review by Single-blind

Peer reviewer comments 3

Editor who approved publication: Dr Martin Bluth

Benjamin Y Lu,1 David Kudlowitz,1, Lawrence B Gardner1–3

1Department of Medicine, 2Department of Biochemistry and Molecular Pharmacology, 3The Perlmutter Cancer Center, NYU Langone Medical Center, NYU School of Medicine, New York, NY, USA

Purpose: Diagnosing heparin-induced thrombocytopenia, a potentially catastrophic immune-mediated disorder, continues to pose significant challenges for clinicians, as both clinical and laboratory tools lack specificity. There is mounting evidence supporting a positive correlation between definitive heparin-induced thrombocytopenia and optical density (OD) positivity from the widely available anti-platelet factor 4 enzyme-linked immunosorbent assays (PF4 ELISAs). However, the clinical features distinguishing these patients remain poorly understood.
Patients and methods: To better characterize this group, we conducted a case-controlled, retrospective chart review of patients from two large, urban academic institutions who underwent a PF4 ELISA at a central laboratory. Associations between OD and 18 clinical characteristics were calculated using the Fisher's exact test for categorical variables and Wilcoxon rank-sum test for continuous variables.
Results: In total, 184 negative patients (OD <0.7), and 121 positive patients (OD >0.7), including 74 low-positive patients (0.7, OD <1.4) and 47 high-positive patients (OD >1.4) were identified. Several clinical variables were significantly different in the negative group compared with the positive group, including hospital day (P<0.001), previous admission within the past 3 months (P<0.001), and the presence of a new thrombus (P=0.003). However, many of these variables were not different between the negative and low-positive group, and were only distinct between the negative and high-positive group. When the low-positive and high-positive groups were compared, only the 4T score was significantly different (P=0.003).
Conclusion: These data indicate that those with OD >1.4 form a distinct clinical group and support the clinical utility of the 4T score.

Keywords: heparin-induced thrombocytopenia, platelet factor 4 ELISA, thrombocytopenia, HIT, heparin

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