title: Interrater agreement for two systems used to determine the probability of heparin-induced thrombocytopenia.
abstract: OBJECTIVE
  The interrater reliability of the 4T's method and the HIT expert probability (HEP) score for clinical evaluation of suspected heparin-induced thrombocytopenia (HIT) was investigated.
  
  
  METHODS
  Patients hospitalized over a three-year period who were tested for HIT via anti-platelet factor 4 (anti-PF4) antigen assay were identified using laboratory data; 127 patient cases met the study inclusion criteria. Nine clinical pharmacists with expertise in HIT management evaluated the 127 cases using two pretest scoring systems: the 4T's score and the HEP score. Each case was independently evaluated using both 4T's and HEP scores. The primary endpoint was interrater agreement of overall 4T's and HEP scores and individual item scores.
  
  
  RESULTS
  Raw agreement of values assigned by the two raters for each of the four items comprising the 4T's score ranged from 0.54 to 0.86, with agreement of 0.63 for final patient categorizations. Raw agreement of rater weightings of the eight HEP scoring items ranged from 0.34 to 1.0; for dichotomization of patients at the suggested screening cutoff value (>2.0), agreement was 0.65. Kappa coefficients were 0.15-0.45 for 4T's item scores and 0.17-0.70 for HEP score item scores. With both scoring systems, low rater agreement mainly related to determination of the timing of thrombocytopenia and possible other causes of the disorder.
  
  
  CONCLUSIONS
  In a retrospective study, inter-rater agreement in scoring of HIT probability via the 4T's and HEP scoring systems was relatively low. The HEP score did not increase interrater reliability or correlation with anti-PF4 antibodies compared with the 4T's score.
authors.affiliation: Maxime Doré, B.Pharm., M.Sc., is Pharmacist, Department of Pharmacy, Hôpital du Sacré-Coeur de Montréal, Montréal, Quebec, Canada. Anne Julie Frenette, B.Pharm., M.Sc., is Assistant Clinical Professor, Associate Researcher, and Critical Care Pharmacist, Department of Pharmacy and Research Center, Hôpital du Sacré-Coeur de Montréal, and Faculty of Pharmacy, University of Montreal. Isabelle Chagnon, M.D., FRCPC, is Specialist, Internal Medicine, Department of Medicine, Hôpital du Sacré-Coeur de Montréal, and Clinical Professor of Medicine, Faculty of Medicine, University of Montreal. Nathalie Routhier, M.D., M.Sc., FRCPC, is Specialist, Internal Medicine, Department of Medicine, Hôpital du Sacré-Coeur de Montréal, and Clinical Professor of Medicine, Faculty of Medicine, University of Montreal. David Williamson, B.Pharm., M.Sc., BCPS, is Associate Researcher and Critical Care Pharmacist, Department of Pharmacy and Research Center, Hôpital du Sacré-Coeur de Montréal, and Associate Clinical Professor, Faculty of Pharmacy, University of Montreal. maxime.dore@umontreal.ca.
authors.forename: Maxime
authors.initials: M
authors.lastname: Doré
authors.affiliation: Maxime Doré, B.Pharm., M.Sc., is Pharmacist, Department of Pharmacy, Hôpital du Sacré-Coeur de Montréal, Montréal, Quebec, Canada. Anne Julie Frenette, B.Pharm., M.Sc., is Assistant Clinical Professor, Associate Researcher, and Critical Care Pharmacist, Department of Pharmacy and Research Center, Hôpital du Sacré-Coeur de Montréal, and Faculty of Pharmacy, University of Montreal. Isabelle Chagnon, M.D., FRCPC, is Specialist, Internal Medicine, Department of Medicine, Hôpital du Sacré-Coeur de Montréal, and Clinical Professor of Medicine, Faculty of Medicine, University of Montreal. Nathalie Routhier, M.D., M.Sc., FRCPC, is Specialist, Internal Medicine, Department of Medicine, Hôpital du Sacré-Coeur de Montréal, and Clinical Professor of Medicine, Faculty of Medicine, University of Montreal. David Williamson, B.Pharm., M.Sc., BCPS, is Associate Researcher and Critical Care Pharmacist, Department of Pharmacy and Research Center, Hôpital du Sacré-Coeur de Montréal, and Associate Clinical Professor, Faculty of Pharmacy, University of Montreal.
authors.forename: Anne Julie
authors.initials: AJ
authors.lastname: Frenette
authors.affiliation: Maxime Doré, B.Pharm., M.Sc., is Pharmacist, Department of Pharmacy, Hôpital du Sacré-Coeur de Montréal, Montréal, Quebec, Canada. Anne Julie Frenette, B.Pharm., M.Sc., is Assistant Clinical Professor, Associate Researcher, and Critical Care Pharmacist, Department of Pharmacy and Research Center, Hôpital du Sacré-Coeur de Montréal, and Faculty of Pharmacy, University of Montreal. Isabelle Chagnon, M.D., FRCPC, is Specialist, Internal Medicine, Department of Medicine, Hôpital du Sacré-Coeur de Montréal, and Clinical Professor of Medicine, Faculty of Medicine, University of Montreal. Nathalie Routhier, M.D., M.Sc., FRCPC, is Specialist, Internal Medicine, Department of Medicine, Hôpital du Sacré-Coeur de Montréal, and Clinical Professor of Medicine, Faculty of Medicine, University of Montreal. David Williamson, B.Pharm., M.Sc., BCPS, is Associate Researcher and Critical Care Pharmacist, Department of Pharmacy and Research Center, Hôpital du Sacré-Coeur de Montréal, and Associate Clinical Professor, Faculty of Pharmacy, University of Montreal.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Chagnon
authors.affiliation: Maxime Doré, B.Pharm., M.Sc., is Pharmacist, Department of Pharmacy, Hôpital du Sacré-Coeur de Montréal, Montréal, Quebec, Canada. Anne Julie Frenette, B.Pharm., M.Sc., is Assistant Clinical Professor, Associate Researcher, and Critical Care Pharmacist, Department of Pharmacy and Research Center, Hôpital du Sacré-Coeur de Montréal, and Faculty of Pharmacy, University of Montreal. Isabelle Chagnon, M.D., FRCPC, is Specialist, Internal Medicine, Department of Medicine, Hôpital du Sacré-Coeur de Montréal, and Clinical Professor of Medicine, Faculty of Medicine, University of Montreal. Nathalie Routhier, M.D., M.Sc., FRCPC, is Specialist, Internal Medicine, Department of Medicine, Hôpital du Sacré-Coeur de Montréal, and Clinical Professor of Medicine, Faculty of Medicine, University of Montreal. David Williamson, B.Pharm., M.Sc., BCPS, is Associate Researcher and Critical Care Pharmacist, Department of Pharmacy and Research Center, Hôpital du Sacré-Coeur de Montréal, and Associate Clinical Professor, Faculty of Pharmacy, University of Montreal.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Routhier
authors.affiliation: Maxime Doré, B.Pharm., M.Sc., is Pharmacist, Department of Pharmacy, Hôpital du Sacré-Coeur de Montréal, Montréal, Quebec, Canada. Anne Julie Frenette, B.Pharm., M.Sc., is Assistant Clinical Professor, Associate Researcher, and Critical Care Pharmacist, Department of Pharmacy and Research Center, Hôpital du Sacré-Coeur de Montréal, and Faculty of Pharmacy, University of Montreal. Isabelle Chagnon, M.D., FRCPC, is Specialist, Internal Medicine, Department of Medicine, Hôpital du Sacré-Coeur de Montréal, and Clinical Professor of Medicine, Faculty of Medicine, University of Montreal. Nathalie Routhier, M.D., M.Sc., FRCPC, is Specialist, Internal Medicine, Department of Medicine, Hôpital du Sacré-Coeur de Montréal, and Clinical Professor of Medicine, Faculty of Medicine, University of Montreal. David Williamson, B.Pharm., M.Sc., BCPS, is Associate Researcher and Critical Care Pharmacist, Department of Pharmacy and Research Center, Hôpital du Sacré-Coeur de Montréal, and Associate Clinical Professor, Faculty of Pharmacy, University of Montreal.
authors.forename: David
authors.initials: D
authors.lastname: Williamson
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000009:adverse effects*; D005260:Female; D006493:Heparin / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010607:Pharmacy Service, Hospital / Q000592:standards*; D010976:Platelet Count; D011237:Predictive Value of Tests; D011336:Probability; D015203:Reproducibility of Results; D013921:Thrombocytopenia / Q000139:chemically induced*
chemical_list: D000925:Anticoagulants; D006493:Heparin