The role of activated partial thromboplastin time-clot waveform analysis in distinguishing positive samples of lupus anticoagulant from hemophilia A.

INTRODUCTION

Clot waveform analysis (CWA) is a technique that continuously monitors changes in light transmittance or absorbance during fibrin clot formation in plasma, enhancing routine clotting test assessment. Patients with Lupus Anticoagulant (LA) and Hemophilia A (HA) both exhibit isolated prolongation of activated partial thromboplastin time (aPTT); however, their management differs significantly. CWA can aid in distinguishing between these conditions, particularly in cases where standard coagulation tests are inconclusive and specialized assays are unavailable.

METHODS

This prospective case-control study included patients with demonstrable LA (n = 69), healthy controls (n = 75) and diseased controls [HA with (n = 16) and without inhibitor (n = 36).

RESULTS

The quantitative data of aPTT-CWA including velocity peak time, acceleration peak time and height of acceleration [-] were significantly lower in LA-positive samples with prolonged aPTT in comparison with HA without inhibitors. The qualitative data comprising Shoulder in 1st derivative, Biphasic wave in 2nd derivative [-] and Serrated wave pattern in 2nd derivative were significantly common in HA samples without inhibitors. In comparison to healthy controls, LA-positive patients with normal aPTT had significantly lower velocity peak time and height of velocity along with higher width of velocity. In acceleration peak time and width of acceleration [-] peak were significantly higher along with lower height of acceleration [+] and height of acceleration [-]. AUROCs of height of acceleration [-], width of acceleration [-] and width of velocity were statistically and biologically significant. The shoulder in 2nd derivative was significantly common in LA-positive samples.

CONCLUSION

The aPTT-CWA has limited utility for differentiating LA positive from HA samples with and without inhibitors. However, aPTT-CWA may help in selecting patients with normal aPTT who merit further confirmatory testing for LA with a compatible history.