Flow cytometry vs conventional methods for the evaluation of anti-PF4/heparin antibodies: a single center study.

Aim: Heparin-induced thrombocytopenia (HIT) is a rare, life-threatening, immune-mediated adverse effect of heparin administration. This study compares frequently used laboratory assays in terms of their effectiveness in HIT diagnosis. Materials & methods: Fifty patients with suspected HIT were tested by gel immunoassay and solid phase PF4/heparin antibody ELISA. On positive results, platelet activation markers P-selectin and Annexin V were assayed using flow cytometry. Results: Thirty/50 patients were negative for both immunoassays. Flow cytometry was performed in the 20 immunoassay positive patients. Platelet activation was observed in 7/20 in the presence of low heparin concentration (0.2 IU/ml). Conclusion: The results are in accordance with the currently available literature and flow cytometry seems a promising alternative in HIT laboratory investigation.

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Evaluation of STic Expert® HIT Kit and Its Comparison with ID-PaGIA™ Test in Suspected Heparin-Induced Thrombocytopenia.

Heparin-induced thrombocytopenia (HIT) is an adverse drug reaction caused by heparin. HIT occurs due to IgG antibodies directed against heparin-bound platelet factor 4 (PF4). The aim of this study was to evaluate the STic® Expert HIT for detection of anti-PF4/heparin antibodies in comparison with ID-PaGIA™ kit. The results were further confirmed by Heparin-induced platelet aggregation test (HIPA). A total of 17 patients with a suspected diagnosis of HIT were enrolled. The 4 T scoring of each case was performed. Testing for HIT was carried out by ID-PaGIA™, STic® Expert HIT, and HIPA. Testing by STic® Expert HIT test demonstrated positivity in three cases while testing by ID-PaGIA™ test kit revealed four positive cases. Two of these cases were confirmed as HIT by HIPA. The study suggests that STic® Expert HIT an equally effective test, in combination with the 4T scoring system for detecting/excluding the diagnosis of HIT. A large number of cases are needed for validation.

Evaluation of a diagnostic algorithm for Heparin-Induced Thrombocytopenia.

INTRODUCTION: Heparin-Induced Thrombocytopenia (HIT) is a rare but serious immune-mediated complication of heparin treatment. HIT is characterized by an acute, transient prothrombotic state combined with thrombocytopenia and is caused by platelet-activating IgG antibodies that bind to complexes of heparin and platelet factor 4. The diagnosis of HIT relies on clinical presentation and the demonstration of HIT antibodies. One approach to improve the efficacy of laboratory analysis is to use a diagnostic algorithm. AIM: To evaluate one diagnostic algorithm for HIT where the 4 T's clinical risk score is combined with immunochemical and/or functional assays. MATERIALS AND METHODS: The quality of the diagnostic algorithm was retrospectively evaluated in 101 patients with suspected HIT. Laboratory results obtained from the diagnostic algorithm were compared to Heparin-Induced Platelet Aggregation (HIPA) and clinico-pathological evaluation of patients' medical records. RESULTS: We found that the algorithm had a diagnostic efficacy of 94%, with specificity of 94% and sensitivity 94%. Positive likelihood ratio (LR+) was 16.0, and the negative likelihood ratio (LR-) 15.5. The efficacy of PaGIA (n=95) was 0.46, and IgG-specific HPF4-abELISA (n=54) was 0.87. CONCLUSIONS: The diagnostic algorithm for HIT is sufficiently accurate and leads to in overall faster results and decreased cost of analysis. The weakest link of the algorithm is the risk of miscalculated 4T's scores, which is inevitably exacerbated by the insufficient experience most clinicians have with HIT. This highlights the importance of clear instructions from the laboratory and coagulation clinic.

Evaluación de un Inmunoensayo de partículas en gel para la determinación de anticuerpos contra Treponema pallidum en donantes de sangre / Evaluation of a particle gel immunoassay for determination of antibodies against Trepanoma pallidum in blood donors

El tamizaje de laboratorio para sífilis está usualmente llevado a cabo por serología. No se observó resultados falsos positivos cuando se utilizó ID-PaGIA y se observó una excelente sensibilidad y especificidad de esta prueba treponérnica. Las ventajas del método son el tiempo de reacción de tan solo 20 minutos, la simplicidad del procedimiento con poco equipo de laboratorio, la posibilidad de realizar lecturas automatizadas y la posibilidad de mantener un record de los resultados y con ello la trazabilidad.

Laboratory diagnosis of syphilis is usually accomplished by serology. No false-positive results were found with ID-PaGIA and compared with other treponemal tests ID-PaGIA has excellent sensitivity and specificity. Advantages of the PaGIA are the fast reaction time of only 20 minutes and the simplicity of the procedure with minimal technical equipment.