Evaluation of Factor XIII Activity Using the Ammonia Release Method with and without Iodoacetamide Sample Blanking Procedure

Abstract

Background: The ammonia release assay is a quantitative factor XIII (FXIII) activity screening test. It is recommended
to perform with a sample blank containing 1 mmol/L iodoacetamide to avoid overestimating caused by
side reactions. We evaluated an ammonia release assay, Berichrome FXIII assay, on the CS-2000i analyzer with
and without sample blank procedures to observe the impact of the side reactions concerning overestimating
FXIII activity. Methods: Plasma samples from 10 suspected FXIII deficiency patients, 30 normal volunteers, 6
diluted human standard plasmas and one FXIII deficient plasma, including normal and abnormal control plasma
were analyzed. All plasma samples were measured twice with and without sample blank procedure in which 1
mmol/L iodoacetamide and physiological saline was added to reagents of the assay, respectively. The results
were corrected by subtracting the values with blank from the values without blank. Results: The means (standard
deviations) of FXIII activity of normal volunteers, with and without the blank procedures, were 98.4% (19.1) and
107.3% (19.5), respectively. In the low range of FXIII activity, the values after blank subtraction were lower than
that without the subtraction by 3% to 7%. Values near normal range seemed not to be affected by the side
reactions. Conclusion: Procedure with a sample blank was recommended to avoid overestimating the results
when using the ammonia release assay to detect FXIII activity.