A preliminary study of platelet hyperactivity in the chronic indeterminate phase of Chagas' disease.

The chronic indeterminate phase of Chagas' disease is asymptomatic despite positive test results for antibodies specific to Trypanosoma cruzi. CD62P-APC (P-selectin) and PAC-1 FITC (GpIIb/IIIa) may improve diagnosis as biomarkers of platelet activity. Nine asymptomatic seropositive subjects, previously untreated, were selected from a blood bank within a year of Chagas' disease detection, in addition to a control group of four. All subjects were evaluated by flow cytometry for CD62P, PAC-1 and CD41, and in a complementary study, by Tissue Doppler Echocardiography for isovolumic relaxation times (IVRT) and E/A ratios. The subjects were classified as positive or negative for CD62P and PAC-1 by a cut off obtained from their mean±2SD. For IVRT and E/A ratios, cut offs were obtained from the American Society of Echocardiography and the European Association of Cardiovascular Imaging recommendations. Fisher's exact test was used for associated findings. Pre-test and post-test probability, sensitivity, specificity, positive and negative predictive values and likelihood ratios were calculated. Abnormalities were expressed as platelet hyperactivity and ventricular dysfunction in CD62P, PAC-1, IVRT and E/A ratios. CD62P appears to have greater sensitivity (0.75) and PAC-1, more accurate specificity (0.75), which may explain thrombotic events in Chagas' disease. We recommend the use of CD62P and PAC-1 as biomarkers of platelet hyperactivity in patients in the chronic indeterminate phase of Chagas' disease.