title: Assay discrepancy in mild haemophilia A: entire population study in a National Haemophilia Centre.
abstract: Assay discrepancy in mild haemophilia, here defined by a significantly higher factor VIII (FVIII):C response by the one-stage procoagulant assay as compared with a two-stage enzymatic method, has repeatedly been reported in literature. The purpose of this study was to determine the overall prevalence of this phenomenon amongst mild haemophilia families from a population of 2.95 million inhabitants in the Western Danish region. Information was collected retrospectively through a thorough search of archives of the National Haemophilia Centre in Aarhus. We identified 109 patients with mild haemophilia A amongst whom 92 were eligible to enter the study. These represent a total of 53 unrelated families. Our data illustrate that this assay discrepancy pattern is found quite frequently amongst our mild haemophilia A families. While the ratio of FVIII:C chromogenic/FVIII:C clot values was quite consistent amongst patients belonging to same family pattern, ratios in the entire cohort of families ranged from 0.18 to 1.00. Selecting a cut-off level for the FVIII:C chromogenic/FVIII:C clot ratios at 0.7, 0.6 and 0.5, respectively, we found that 38 (72%), 27 (51%) and 19 (36%) of families, respectively, displayed this assay discrepancy. In 10 patients, the FVIII:C chromogenic level was inside the category of moderate haemophilia at >0.01-<0.05 IU mL(-1), pointing to a class-shift in the biochemical phenotype. In conclusion, our data illustrate a substantial prevalence of the assay discrepancy phenomenon amongst mild haemophilia A patients in our geographical area.
authors.affiliation: Faculty of Health Sciences, Aarhus University, Aarhus, Denmark.
authors.forename: A L
authors.initials: AL
authors.lastname: Poulsen
authors.forename: L H
authors.initials: LH
authors.lastname: Pedersen
authors.forename: A-M
authors.initials: AM
authors.lastname: Hvas
authors.forename: L H
authors.initials: LH
authors.lastname: Poulsen
authors.forename: H
authors.initials: H
authors.lastname: Thykjaer
authors.forename: J
authors.initials: J
authors.lastname: Ingerslev
mesh_terms: D001780:Blood Coagulation Tests / Q000379:methods; D002863:Chromogenic Compounds; D005169:Factor VIII / Q000032:analysis*; D006467:Hemophilia A / Q000097:blood* / Q000235:genetics; D006801:Humans; D008297:Male; D018579:Patient Selection; D015203:Reproducibility of Results
chemical_list: D002863:Chromogenic Compounds; D005169:Factor VIII