Measurement of FVIII:C Level by Clot Waveform Analysis

Kim, Soon Ki; Jung, Soo Young; Yoo, Ki Young; Park, Sang Kyu; Choi, Yong Mook

Abstract

BACKGROUND
By using ACL 9000 coagulation analyzer (Instrumentation Laboratory Co., Lexington, Massachusetts, USA), we tried to investigate the possibility that activated partial thromboplastin time (aPTT) clot waveform analysis (CWA) may provide additional information on patients with hemophilia A.
METHODS
Plasma samples were obtained from 35 patients with hemophilia A. The factor VIII levels of those patients were measured by a conventional one-stage factor VIII:C clotting assay and a factor VIII antigen assay. The data were applied to a Microsoft excel program calculating the index of the second derivative, and the time at point b (Min2), the point in time that clotting is initiated was also calculated.
RESULTS
The corresponding aPTT clotting times were prolonged in all 9 patients with severe hemophilia A. The CWA could further discriminate between different levels of FVIII:C in the patients (n=20), with a FVIII:C level <4 IU/dL by conventional assay. The correlation between FVIII:C and the recalculated aPTT using Min2 was very high in patients with FVIII:C < or =4 IU/dL (r=0.952). Among the 9 patients who showed a lot of discrepancy from the FVIII:C level, there was 8 patients with mild hemophilia and 1 patient with moderate hemophilia (FVIII:C level 4.5%).
CONCLUSION
Our study suggested that CWA and Min2 values might have greater discriminatory power in assessing low clotting factor activity. Further study is needed, including more patients with hemophilia A using CWA, correlation according to the severity group, a lower limit of detection for VIII:C, and a multiple one-stage assay.