The timing of a positive test result for heparin-induced thrombocytopenia relative to the platelet count and anticoagulant therapy in 43 consecutive cases

Majed A. Refaai, Elizabeth M. Van Cott, Michael Laposata

Research output: Contribution to journalArticle

9 Scopus citations


We studied the timing of a positive heparin-induced thrombocytopenia (HIT) test result relative to changes in platelet count and anticoagulant use. We obtained platelet counts in 100 consecutive HIT+ cases before, during, and after heparin therapy; 43 cases met study criteria and were included in study part 1. In part 2, platelet counts at the time of the HIT test in 2 groups (100 each HIT+ and HIT-cases) were compared. In part 1, cases could be divided into 4 groups based on the diagnosis of HIT relative to platelet counts (1, within 1-2 days of a major drop in platelet count [11.6%]; 2, after >2 days of a majorfall in platelet count [41.9%]; 3, in patients with already low platelet counts [27.9%]; 4, after platelet count was rising [18.6%]). In study part 2, the mean platelet counts for the HIT+ and HIT-groups were almost identical. HIT should be suspected in any thrombotic patient who had a previous decline in platelet count, has a low platelet count, or has a rising platelet count after a previous decline in association with heparin exposure. In study part 2, 1 platelet count value at the time of the HIT test did not provide useful information.

Original languageEnglish (US)
Pages (from-to)497-504
Number of pages8
JournalAmerican Journal of Clinical Pathology
Issue number4
StatePublished - Apr 1 2003
Externally publishedYes



  • Heparin
  • Heparin-induced thrombocytopenia
  • Platelet count
  • Thrombocytopenia
  • Thrombosis

ASJC Scopus subject areas

  • Pathology and Forensic Medicine

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