Relationship between the 4 T s scoring system and the antiplatelet factor 4/heparin antibodies test in critically ill patients

Aim Heparin‐induced thrombocytopenia ( HIT ) is an adverse drug reaction and potentially progresses to fatal thrombosis. The 4 T s scoring system has been reported as a clinical pretest for HIT . However, its usefulness in critically ill patients has not yet been thoroughly examined. Thus, we evaluated the clinical usefulness of the 4 T s score in the diagnosis of HIT in critically ill patients. Methods One hundred and four critically ill patients who were admitted to our intensive care unit and who underwent the antiplatelet factor 4/heparin complex antibodies ( PF 4/heparin Ab ) test with suspected HIT were enrolled in the study. The primary endpoint variable was the 4 T s score. The secondary endpoint variables were laboratory data, length of stay, and mortality, compared between the PF 4/heparin Ab positive and negative groups. Results There was no significant difference in the 4Ts scores between the PF 4/heparin Ab positive and negative groups. The positive predictive value ( HIT patients/4 T high score patients) was 15.4% (2/13), the negative predictive value (non‐ HIT patients/4 T low score patients) was 87.5% (42/48), and the false‐negative rate for the 4 T s score (4 T low score patients/ HIT patients) was as high as 54.5% (6/11). The PF 4/heparin Ab positive patients had longer stay in intensive care compared to the PF 4/heparin Ab negative patients ( P  = 0.035). Conclusions The present study showed the discrepancy between the 4 T s score and PF 4/heparin Ab . When HIT is suspected in critically ill patients, an immediate HIT antibody test and initiation of therapeutic management of HIT are required regardless of the 4 T s score.