title: 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).
abstract: 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
authors.affiliation: Department of Pediatrics, Nara Medical University, Kashihara City, Japan. mshima@naramed-u.ac.jp
authors.forename: Midori
authors.initials: M
authors.lastname: Shima
authors.forename: Tomoko
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Fukuda
authors.forename: Youko
authors.initials: Y
authors.lastname: Kubota
authors.forename: Ichiro
authors.initials: I
authors.lastname: Tanaka
authors.forename: Katumi
authors.initials: K
authors.lastname: Nishiya
authors.forename: Alan R
authors.initials: AR
authors.lastname: Giles
authors.forename: Akira
authors.initials: A
authors.lastname: Yoshioka
mesh_terms: D001780:Blood Coagulation Tests / Q000295:instrumentation / Q000592:standards; D005169:Factor VIII / Q000032:analysis*; D006467:Hemophilia A / Q000097:blood / Q000175:diagnosis; D006801:Humans; D007700:Kinetics; D010314:Partial Thromboplastin Time; D012016:Reference Values; D012680:Sensitivity and Specificity
chemical_list: D005169:Factor VIII