Evaluation of a rapid immunochromatographic diagnostic test for heparin-induced thrombocytopenia: validation of delayed test and whole blood test.

Heparin-induced thrombocytopenia (HIT) is a rare, iatrogenic condition, characterized by its potential severity and diagnostic difficulties. There are rapid diagnostic tests for suspected HIT. Among these, the STic Expert® HIT has a good sensitivity to detect HIT. However, it must be performed within 2 h after sampling. The aim of this study was to evaluate a delayed STic Expert® HIT test in plasma and whole blood. Thirty-six patients were prospectively included for HIT testing delayed analysis and 64 for whole blood analysis. For any request for HIT testing, an analysis by STic Expert® HIT was performed within 2 h and 8 h post-sampling. Any positive result was confirmed by a functional test, platelet aggregation with heparin, release of 14C-serotonin assay (SRA), and immunological assay for anti-platelet factor 4 IgG antibodies. Among the 36 patients for delayed analysis, 20 had an initially positive STic Expert® HIT test. Among the 64 patients for whole blood analysis, 20 had an initially positive STic Expert® HIT test, and 24 positives in whole blood. For the test performed at T0, Se = 100 %, Sp = 68.4 %, PPV = 73.9 %, and NPV = 100 %. The Chi-square (X2) = 18.2 with p < 0.001. For the test performed at T = 8 h, Se = 100 %, Sp = 68.4 %, PPV = 73.9 %, and NPV = 100 %. The X2 = 18.2 with p < 0.001. For the test performed in whole blood, Se = 100 %, Sp = 74.4 %, PPV = 37.5 %, and NPV = 100 %. The X2 = 18.6 with p < 0.001. In conclusion, we have demonstrated that the STic Expert® can be used to perform an HIT diagnostic test 8 h after sampling and on whole blood. However, this study needs to be confirmed on a larger number of samples.