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


METHODS
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.


RESULTS
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).


CONCLUSIONS
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.
Pharmacy Services, Mayo Clinic, Rochester, MN.
Mallory A
MA
Fiorenza
Pharmacy Services, Mayo Clinic, Rochester, MN.
Erin N
EN
Frazee
Pharmacy Services, Mayo Clinic, Rochester, MN.
Heather A
HA
Personett
Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN.
Ross A
RA
Dierkhising
Pharmacy Services, Mayo Clinic, Rochester, MN. Electronic address: schramm.garrett@mayo.edu.
Garrett E
GE
Schramm
D000328:Adult; D000368:Aged; D000906:Antibodies / Q000097:blood; D000925:Anticoagulants / Q000009:adverse effects*; D001779:Blood Coagulation Factors / Q000276:immunology*; D016022:Case-Control Studies; D016638:Critical Illness; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D006493:Heparin / Q000009:adverse effects*; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011336:Probability; D012372:ROC Curve; D012189:Retrospective Studies; D013921:Thrombocytopenia / Q000139:chemically induced* / Q000175:diagnosis / Q000276:immunology
D000906:Antibodies; D000925:Anticoagulants; D001779:Blood Coagulation Factors; C037685:platelet factor V; D006493:Heparin
Clinical scoring system; Critical care; Heparin-induced thrombocytopenia; Intensive care unit; Optical density; Thrombocytopenia