[Anti-PF4 antibodies and thrombophlebitis in a child with cerebral venous thrombosis]. / Anticorps anti-PF4 et thrombopénie chez un enfant avec thrombophlébite cérébrale.

We report the case of a 13-year-old girl, with a cerebral venous thrombosis treated initially by heparin. In front of this early thrombocytopenia, in spite of the absence of preliminary treatment by heparin, the "heparin-dependent" anti-PF4 antibodies ELISA assay was realized and turned out to be strongly positive. In spite of the negativity of the specific functional tests, the heparinotherapy was substituted by a treatment by danaparoïd of sodium, allowing a clinico-biological improvement. Because of the low score of HIT imputability, we realized a specific antibodies anti-PF4 alone assay which was strongly positive. This specific positivity probably explains the positivity of the antibodies anti PF4 "heparin-dependent" assay. The originality of this case lies in the young age of the patient and in the probably pathogenic character of these unusual antibodies, in addition markers of an auto-immune disease.

PFA-100 and flow cytometry: can they challenge aggregometry to assess antiplatelet agents, other than GPIIbIIIa blockers, in coronary angioplasty?

INTRODUCTION: Platelet response to inhibitors varies widely, leading to a higher risk of abrupt closure events in insufficiently treated-coronary heart disease patients. The aim of this study was to compare, in patients under various antiplatelet regimens, three platelet function assays: aggregometry, PFA-100 and flow cytometry. These assays stand for available tests, as "ready-to-use" device (PFA-100) and sophisticated assay (cytometry). We chose the setting of percutaneous coronary intervention as a standardized procedure to determine which test was appropriate to detect the effect of (1) an aspirin bolus in patients under long-term aspirin treatment, and (2) ticlopidin in case of stent implantation. METHODS: Fifty patients under oral aspirin treatment were randomized to receive a bolus of 500 mg aspirin before angioplasty (n=25). Ticlopidin was given at a 500 mg loading dose in the case of stent implantation (n=38). Platelet function was assessed before, at 2 and 24 h after angioplasty. RESULTS: Considering aspirin antiplatelet effect, the following was observed: (1) a lack of further inhibition after the bolus whatever assay was used and (2) a disagreement between aggregometry and PFA-100 to classify patients as being poor or good aspirin responders (kappa were 0.11 and 0.28 between ADP 4 or 6 microM aggregation, respectively, and PFA-100). Another finding was the good performance of flow cytometry, which evaluated GPIIbIIIa activation, and aggregometry, to detect ticlopidin the day after the loading dose. In contrast, PFA-100 was insensitive to ticlopidin. CONCLUSION: Current assays are not interchangeable to monitor antiplatelet treatment in daily practice.