A clinical audit of congenital thrombophilia investigation in tertiary practice

BACKGROUND: The presumed cause of congenital thrombophilia can now be explained in ~50% of familial thrombosis cases following evaluation of a range of markers, primarily comprising factor V Leiden (FVL), activated protein C resistance (APCR), protein C (PC), protein S (PS) and antithrombin (AT). However, the effectiveness of such evaluations is largely determined by limiting improper investigations, either in inappropriate patients or at unsuitable timepoints.

AIM: To evaluate clinical ordering patterns for a range of thrombophilia associated tests at a tertiary level public facility.

METHODS: Several independent audits into clinical requests for FVL, APCR, PC, PS, and AT testing were performed at our institution.

RESULTS: We identified a wide variety of clinical ordering background, although most requests related to 'thrombosis' or 'obstetric' indications. For FVL, the detection rate of heterozygotes continues to decline and is currently ~10% of investigations. For APCR, review of clinical requests and clinical notes indicated that around 36% of investigations occurred whilst patients were on anticoagulant therapy. For PC, PS and AT investigations, additional testing of samples that yielded low test results for PC, PS and/or AT indicated that an alarming 80% of these cases likely derived from patients on anticoagulant therapy.

CONCLUSION: These results continue to reflect on poor patient or timing selection for congenital thrombophilia investigations that compromises the utility of these tests. In total, this would yield a very high rate of false positive identification for disorders that patients do not have, raising the question: are broadly based congenital thrombophilia investigations doing more harm than good?