Japanese collaborative study to assess inter-laboratory variation in factor VII activity assays.
BACKGROUND
The clinical phenotype manifest by patients with factor VII (FVII) deficiency correlates poorly with that predicted by laboratory tests. Despite its importance, there are no data on the variability of inter-laboratory determinations of low to very low plasma FVII activity (FVII:C).


METHODS
We distributed three FVII-deficient plasma samples, prepared by immunoaffinity chromatography, to 58 laboratories in Japan. All samples were assayed using standardized reference plasma as a calibrator. Recombinant thromboplastin was also supplied as a common reagent.


RESULTS
In the case of sample A, which had a very low FVII:C, the use of standardized reference plasma and thromboplastin, lowered the variability of inter-laboratory measurements, when compared with the variability observed when samples were assayed using the respective laboratory's routine method.


CONCLUSIONS
The data obtained indicated that results for samples with a very low FVII:C were greatly influenced by the number of plasma dilutions used in constructing a standard activity curve, and also by the type of calibrator and thromboplastin. Such variability was not seen for samples with moderate FVII:C. We conclude that it is necessary to develop a more sensitive and accurate FVII:C measurement system for the diagnosis and treatment of FVII deficiency.
Takamiya
O
O
Department of Biomedical Laboratory Sciences, School of Health Sciences, Shinshu University, Matsumoto, Japan. itosamu@gipac.shinshu-u.ac.jp
Ishikawa
S
S
Ohnuma
O
O
Suehisa
H
H
Iijima
K
K
Kayamori
Y
Y
Bando
S
S
Higashi
K
K
D002138:Calibration; D002624:Chemistry, Clinical / Q000379:methods*; D002846:Chromatography, Affinity / Q000379:methods; D019411:Clinical Laboratory Techniques; D005167:Factor VII / Q000378:metabolism*; D005168:Factor VII Deficiency / Q000175:diagnosis; D006801:Humans; D007564:Japan; D007753:Laboratories; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013925:Thromboplastin / Q000096:biosynthesis / Q000737:chemistry
D005167:Factor VII; D013925:Thromboplastin