Journal of Critical Care
Volume 25, Issue 2 , Pages 287-293, June 2010

The 4Ts scoring system for heparin-induced thrombocytopenia in medical-surgical intensive care unit patients☆

  • Mark Andrew Crowther, MD, MSc

      Affiliations

    • Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario Canada
    • Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario Canada
    • Corresponding Author InformationCorresponding author. St. Joseph's Hospital, Hamilton, Ontario, Canada L8N 4A6. Tel.: +1 905 521 6024; fax: + 1 905 540 6568.
    • ,
  • Deborah J. Cook, MD, MSc

      Affiliations

    • Department of Medicine, McMaster University, Hamilton, Ontario Canada
    • ,
  • Martin Albert, MD

      Affiliations

    • Pharmacy Department (DW) and Department of Medicine (MA,YS,SL), Université de Montréal, Montréal, Quebec, Canada
    • ,
  • David Williamson, MD

      Affiliations

    • Pharmacy Department (DW) and Department of Medicine (MA,YS,SL), Université de Montréal, Montréal, Quebec, Canada
    • ,
  • Maureen Meade, MD, MSc

      Affiliations

    • Department of Medicine, McMaster University, Hamilton, Ontario Canada
    • Department of Clinical Epidemiology and Biostatisitics, McMaster University, Hamilton, Ontario Canada
    • ,
  • John Granton, MD

      Affiliations

    • Department of Medicine, University of Toronto, Toronto, Canada
    • ,
  • Yoanna Skrobik, MD

      Affiliations

    • Pharmacy Department (DW) and Department of Medicine (MA,YS,SL), Université de Montréal, Montréal, Quebec, Canada
    • ,
  • Stephan Langevin, MD

      Affiliations

    • Department of Medicine, Laval University, Quebec, Canada
    • ,
  • Sangeeta Mehta, MD

      Affiliations

    • Department of Medicine, University of Toronto, Toronto, Canada
    • ,
  • Paul Hebert, MD

      Affiliations

    • Department of Medicine, University of Ottawa, Ottawa, Ontario Canada
    • ,
  • Gordon H. Guyatt, MD

      Affiliations

    • Department of Medicine, McMaster University, Hamilton, Ontario Canada
    • Department of Clinical Epidemiology and Biostatisitics, McMaster University, Hamilton, Ontario Canada
    • ,
  • William Geerts, MD

      Affiliations

    • Department of Medicine, University of Toronto, Toronto, Canada
    • ,
  • Christian Rabbat, MD

      Affiliations

    • Department of Medicine, McMaster University, Hamilton, Ontario Canada
    • ,
  • James Douketis, MD

      Affiliations

    • Department of Medicine, McMaster University, Hamilton, Ontario Canada
    • ,
  • Nicole Zytaruk, RN

      Affiliations

    • Department of Medicine, McMaster University, Hamilton, Ontario Canada
    • ,
  • Joanne Sheppard

      Affiliations

    • Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario Canada
    • ,
  • Andreas Greinacher, MD

      Affiliations

    • Department of Immunology and Transfusion Medicine, Ernst-Moritz-Arndt-University-Greifswald, Greifswald, Germany
    • ,
  • Theodore E. Warkentin, MD

      Affiliations

    • Department of Medicine, McMaster University, Hamilton, Ontario Canada
    • Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Ontario Canada
    • ,
  • For the Canadian Critical Care Trials Group

published online 11 February 2010.

Abstract 

Background

Heparin-induced thrombocytopenia (HIT) is commonly considered but rarely confirmed in critically ill patients. The 4Ts score (Thrombocytopenia, Timing of thrombocytopenia, Thrombosis, and oTher reason) might identify individual patients at risk of having this disorder.

Objective

The aim of the study was to evaluate the value of the 4Ts HIT score in comparison with the serotonin-release assay (SRA) in critically ill patients.

Methods

This study describes the combined results of 3 prospective studies enrolling critically ill patients who were investigated for HIT if platelets fell to less than 50 × 109/L or if platelet counts decreased to less than 50% of the value upon intensive care unit admission. We confirmed HIT by a positive platelet SRA. We assigned a 4Ts score blinded to SRA results to all 50 patients investigated for HIT; those with positive SRA results were scored in duplicate.

Results

Of 528 patients, 50 (9.5%) were investigated for HIT; 39 (78%) of 50 (64%-88%) of these patients were scored as “low probability” by 4Ts score and none had a positive SRA. Of 49 patients who underwent SRA testing because of thrombocytopenia, only 2 (4.1%; 0.5-14.0) had a positive SRA (1 with a moderate 4Ts score and 1 with a high 4Ts score). Therefore, the overall incidence of HIT confirmed by SRA was 2 (0.4%) of 528 (0.04%-1.4%).

Conclusions

Significant thrombocytopenia during heparin administration occurred in 9.5% of critically ill patients, but HIT was confirmed in only 4.1% of those undergoing testing, for an overall incidence of 0.4%. A low 4Ts score occurred in 78% of patients investigated for HIT; none of these patients had a positive SRA. We conclude that HIT is uncommon in critically ill patients and that the 4Ts score is worthy of further evaluation in this patient population.

Keywords: Heparin-induced thrombocytopenia, Thrombosis, Cohort study, Intensive care, Heparin, Low-molecular-weight heparin

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☆ Conflict of interest statement: Andreas Greinacher is a consultant for Schering-Plough (Whitehouse Station, NJ, USA) (drug Orgaran); Mitsubishi Pharma (Osaka, Japan) (drug Argatroban); and has received speakers honoraria from Schering-Plough, Mitsubishi Pharma, GlaxoSmithKline (Brentford, Middlesex, USA). Dr Rabbat has acted as a consultant to Pfizer Inc. Dr Crowther has received speaker fees from Bayer (Pittsburgh, PA, USA), Boehringer Ingelheim (Ingelheim am Rhein, Germany), Sanofi-Aventis (Bridgewater, NJ, USA), Pfizer (New York, NY), Leo Laboratories (Copenhagen, Denmark), and Organon (Wyeth); has received unrestricted research funds from Leo Laboratories; and has acted as a consultant for Bayer, Boehringer Ingelheim, Sanofi Aventis, Pfizer, Leo Laboratories, and Organon (Schering-Plough). Dr Warkentin has acted as a consultant for Genetic Testing Institute (GTI) Inc (Waukesha, WI, USA); GlaxoSmithKline; Organon Inc (part of Schering-Plough); and Pfizer Canada. He has received speaking fees from GlaxoSmithKline and Sanofi-Aventis. He has provided paid expert testimony on topic of heparin-induced thrombocytopenia and has received research funding from GTI Inc, GlaxoSmithKline, and Organon Inc (part of Schering-Plough).

PII: S0883-9441(10)00006-7

doi:10.1016/j.jcrc.2009.12.006

Journal of Critical Care
Volume 25, Issue 2 , Pages 287-293, June 2010

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