Determination of coagulation factor VIII activity by a chromogenic substrate method on STA, an automated coagulation analyzer

Abstract

This study was aimed at evaluating the performance of a chromogenic factor VIII assay on STA, an automated coagulation analyzer. Additionally, a correlation study was conducted with an aPTT-based one-stage factor VIII clotting assay. Throughout the study the performance of the chromogenic assay was tested in two ranges of factor VIII activity: a high range with activity between 20% and 150% and a low range with activity below 20%. Inter-assay coefficient of variation ranged from 1.9% to 8.9% and intra-assay coefficient of variation from 0.5% to 11.4%, depending on factor VIII concentration. Day-to-day reproducibility was tested over a 5-day period; between-day imprecision ranged from 7.1% to 9.4%. The chromogenic factor VIII assay showed a good correlation with the clotting assay in both ranges. The correlation coefficients were 0.924 and 0.792 for the high and low range, respectively. A statistically significant difference in mean values was observed in the high range (p < 0.0001). Comparison between the chromogenic assay on STA versus on microplates showed a high correlation (0.991), which was highly significant (p < 0.0001). In conclusion, the chromogenic assay for factor VIII on STA shows good analytical performance. It correlates well with the one-stage factor VIII clotting assay, although significant differences between individual samples occur. Probably these are partly related to differences in measurement principle and standardization. Altogether, this precise and rapid assay is suitable for determination of factor VIII by an automated procedure.

Performance evaluation of Revohem™ FVIII chromogenic and Revohem™ FIX chromogenic in the CS‐5100 autoanalyser

“…Several studies have compared CSA with OSA in FVIII determinations . However, most investigated response to FVIII concentrates in haemophilia patients or FVIII concentrate‐spiked samples.…”

“…11 Several studies have compared CSA with OSA in FVIII determinations. [12][13][14] However, most investigated response to FVIII concentrates in haemophilia patients or FVIII concentrate-spiked samples. To assess variations in determination of FVIII concentrates, "endogenous" FVIII activity should be evaluated by both CSA and OSA, and characteristics of the reagents should be clarified in advance.…”

Evaluation of three automated chromogenic FVIII kits for the diagnosis of mild discrepant haemophilia A

“…Two previous reports have assessed the performance of automated chromogenic assays, using reagents from Chromogenix and an STA analyser, and compared it with the one-stage clotting assay (Kleinveld et al, 1999;Chandler et al, 2003). Both reports showed good precision for the chromogenic assay, and good correlation with one-stage results, but the discrepant haemophilia phenotype was not considered in either of them (Kleinveld et al, 1999;Chandler et al, 2003).…”

Measurement of Hemostatic Factors in EDTA Plasma

“…On the other hand, FVIIIc in citrate plasma was higher than FVIIIag measured in citrate or EDTA plasma, and the correlation coefficient was only 0.61 between the clotting assay and the antigen assay. FVIII levels more than 1.0 U/dL in the FVIII clotting assay were found to correlate imperfectly with levels measured by a chromogenic substrate assay for FVIII 11. Although it is possible that some activation of FVIII occurs during sample collection, storage, or assay, a more likely explanation is that the higher values again reflect a problem with assay standardization.…”

“…This result likely reflects the different standards used for each method. Kleinveld et al11 suggest that the differences among the various assays are probably due to intercompany variations in standardization rather than to differences attributable to the anticoagulant. On the other hand, FVIIIc in citrate plasma was higher than FVIIIag measured in citrate or EDTA plasma, and the correlation coefficient was only 0.61 between the clotting assay and the antigen assay.…”