A clot waveform analysis-based system for differential diagnosis of prolonged activated partial thromboplastin time in plasma samples.

Introduction: Prolonged activated partial thromboplastin time (aPTT) in plasma samples requires quick and accurate differential diagnosis. We developed two methods using clot waveform analysis (CWA) for plasma samples with prolonged aPTT, particularly for factor (F)VIII deficiency. One method estimates FVIII activity (FVIII:C) using CWA without measuring FVIII:C by template matching. The other utilizes CWA in the mixing test to quickly differentiate FVIII deficiency (FD), FVIII inhibitor (Inh), and lupus anticoagulant (LA).

Aim: To establish a more accurate system for differential diagnosis of aPTT prolongation, including FIX deficiency, by combining a CWA-based mixing test and template matching.

Methods: Samples with FD (n = 96), LA (n = 19), and Inh (n = 28) were incubated with normal plasma. FD, LA, and Inh were differentiated using a mixing test, followed by CWA-based template matching.

Results: In the mixing test, sensitivity for FD, Inh, and LA was 100%, 93%, and 100%, and specificity was 96%, 100%, and 100%. Samples with FIX inhibitor (> 0.6 BU/mL) were differentiated as the inhibitor sample. In template matching, almost all severe hemophilia A and B were judged as the respective severe types.

Conclusion: This novel CWA-based measurement system could aid in differential diagnosis of prolonged aPTT.