Abstract
To evaluate the utility of the 4Ts clinical scoring system as a pretest probability method for detection of heparin-induced thrombocytopenia (HIT). Medical and surgical inpatients and outpatients at Kasr El Eini hospital. This single-centre series of 50 HIT testing referrals assessed combination of clinical score (thrombocytopenia, timing, thrombosis, other causes of thrombocytopenia not evident; 4T's), Heparin platelet factor 4 (H-PF4) rapid particle gel immunoassay (PaGIA) and 14C serotonin release assay (SPA) to develop a practical and well tolerated diagnostic strategy for HIT. Sixteen patients (32%) had a low 4T's score, 26 (52%) had an intermediate score and only eight (16%) had a high score. A positive H-PF4 by PaGIA was seen in seven patients (14%). As might be anticipated, the likelihood of obtaining a positive H-PF4 by PaGIA increased with an increasing clinical score, with positive H-PF4 by PaGIA results in low, intermediate and high scoring patients of 6.25, 7.7 and 50%, respectively. The positive predictive value of a positive PaGIA was 92%. The negative predictive value was 100%. Five patients (10%) in our cohort had a positive SRA. All patients with a positive SRA were included in the intermediate (two of 26 patients, 7.7%) or high (three of eight patients, 37.5%) score groups. The negative predictive value of a low 4T's score was 100%, effectively ruling out HIT. A low 4Ts score supports low probability of HIT based on the results of the PaGIA and SRA. Overall, the interrater reliability of the scoring system was fair. Blood Coagul Fibrinolysis 22:701-705 (C) 2011 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins.