Background: Presence of lupus anticoagulant (LA) in the plasma sample may interfere in factor VIII (FVIII) level determination.

Aims: The aim was to compare the results of FVIII activity assay obtained by coagulometric and chromogenic methods. Furthermore, an attempt to demonstrate the impact of LA on the methods used was made.

Methods: A retrospective analysis of a group of 31 patients (median age 39; 19-89) with LA confirmed by the methods recommended by SSC/ISTH was performed. The control group consisted of 38 healthy volunteers (median age 39; 25-68). Measurements were conducted according to the manufacturer´s instructions.

Results: The mean values of factor VIII activity obtained by I-stage clotting and chromogenic methods between the control and study group were compared. The mean FVIII clotting activity in the study group differed significantly from the control group where it was almost 3-fold higher (48.3±9.2 vs 136.6±37.5; p=0.00001). Results obtained using the chromogenic method did not show a statistically significant difference in the activity of FVIII between the compared groups (p< 0.05).

Conclusions: The FVIII level measured using I-stage clotting assay was decreased due to lupus anticoagulant, while using undiluted plasma of the patients. Serial dilution of the plasma caused a linear increase in the FVIII level. This phenomenon was not observed when using chromogenic assay – FVIII level was not decreased although LA was also present in plasma of the patients.
The more significant dependence between the presence of LA and FVIII activity obtained by the coagulation method than the chromogenic method may indicate that the coagulation method is more susceptible to interference from LA. It seems that the determination of FVIII activity in samples of patients with positive LA by chromogenic assay may help to avoid a false positive result. The chromogenic method may be helpful in deciding on therapeutic recommendations for patients with LA undergoing surgery.

[Table 1. Comparison of mean factor VIII activity level in study and control group using chromogenic and coagulometric assay.]

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/comparative-analysis-of-the-coagulometric-and-chromogenic-methods-for-the-determination-of-factor-viii-activity-in-the-plasma-of-patients-suspected-with-blood-coagulation-disorders/