Table 2.

Characteristics of various assays for heparin induced thrombocytopenia syndrome

	4T score ≤ 3[73-76]	ELISA[77]	IgG specific ELISA[77]	OD cut off ≥ 1.0[78]	Heparin confirmation step for IgG specific ELISA[79]	Serotonin release assay[80]	Whole blood impedence Aggregometry[44]
Sensitivity	-	100%	100%	80%	94%	100%	90.3%-93.6%
Specificity	-	81%	89%	85%	90%-93%	95%-97%	89%-96%
PPV	-	28%	40%	42%	45%	NA	84.4%-94.8%
NPV	100%	100%	100%	84%	99.50%	NA	-

PPV: Positve predictive value; NPV: Negative predictive value; NA: Not applicable as serotonin release assay is the gold standard assay for diagnosis of heparin induced thrombocytopenia syndrome.