TESTING FOR PASSOVOY DEFECT IN CHILDREN WITH PROLONGED ACTIVATED PARTIAL THROMBOPLASTIN TIME (APTT)

Purpose: To investigate the value of testing for Passovoy defect using the commercially available Passovoy trait plasma (PTP) in children wi th prolonged activated partial thromboplastin time (APTT). Patients an d Methods: We studied 13 children with prolonged APTT that corrected i n a 1:1 mix with normal human plasma but not with PTP. In most childre n, a thorough laboratory investigation of the intrinsic pathway factor s and von Willebrand factor was performed. Results: Five patients had bleeding manifestations and eight were asymptomatic. Measurement of vo n Willebrand factor and intrinsic pathway factors revealed abnormal va lues in eight patients (low von Willebrand activity in six patients, l ow factor XII in one patient, and the presence of lupus anticoagulant in one patient). Conclusion: Our data suggest inability to diagnose Pa ssovoy defect based on a mixing study. This study also raises the ques tion of whether Passovoy defect exists as a distinct coagulation disor der.