The utility of activated partial thromboplastin time (aPTT) clot waveform analysis in the investigation of hemophilia A patients with very low levels of factor VIII activity (FVIII:C)

• Published in: Thrombosis and haemostasis Vol. 87; no. 3; p. 436
• Main Authors: Shima, Midori, Matsumoto, Tomoko, Fukuda, Kazuyoshi, Kubota, Youko, Tanaka, Ichiro, Nishiya, Katumi, Giles, Alan R, Yoshioka, Akira
• Format: Journal Article
• Language: English
• Published: Germany 01.03.2002
• Subjects: Blood Coagulation Tests - instrumentation; Blood Coagulation Tests - standards; Factor VIII - analysis; Hemophilia A - blood; Hemophilia A - diagnosis; Humans; Kinetics; Partial Thromboplastin Time; Reference Values; Sensitivity and Specificity
• ISSN: 0340-6245
• DOI: 10.1055/s-0037-1613023

The lower detection limit of the conventional one-stage aPTT based clotting assay for determining FVIII:C levels is generally 1.0-2.0 IU/dl. Consequently, it has been impossible to study the clinical significance of levels of FVIII:C less than 1.0 IU/dl. Using a photo-optical automated coagulation analyzer, the Organon Teknika MDA II, we have performed qualitative and quantitative aPTT waveform analysis and measured FVIII:C levels by automated one-stage aPTT clotting assay in 36 severely affected Hemophilia A patients. Qualitative waveform analysis showed clear evidence of individual differences in the waveform profile suggesting differing coagulant activity from patient to patient. The FVIII:C level was less than 0.2 IU/dl in 23 cases and levels of FVIII:C between 0.2 and 1.0 IU/dl could be discriminated in 13 patients. The FVIII:C level in these patients was closely correlated with the minimum value of the second derivative of the aPTT waveform (Min2). This is a measure of the acceleration of change in optical transmission at the initiation of coagulation. Furthermore, the correlation of the