Analysis of the Interference Effects of Ethamsylate on the Determination of Serum Creatinine Levels Using Two Methods.

Background: Accurate quantification of serum creatinine is clinically essential for evaluating renal function. The aim of this study was to investigate the interference of ethamsylate in the detection of serum creatinine via the sarcosine oxidase method and the picric acid method.

Methods: Thirty fresh serum samples with gradient concentrations of creatinine were collected from patients in our hospital. In accordance with CLSI EP7-A2, paired difference experiments and dose-response experiments were conducted to detect serum creatinine by the sarcosine oxidase method and the picric acid method, respectively. In addition, the interference of ethamsylate on the detection of serum creatinine at different concentrations was observed to compare the interference effect of ethamsylate on the detection of serum creatinine by the sarcosine oxidase method and picric acid method.

Results: Paired difference tests revealed that 0.3 g/L ethamsylate significantly negatively affected the determination of creatinine at low, medium, and high creatinine concentrations via the sarcosine oxidase method, and the interference values were -53.67 μmol/L, -93.33 μmol/L, and -318.33 μmol/L, respectively. There was positive interference in the determination of low-concentration creatinine by the picric acid method; the interference value was 7.67 μmol/L, but there was no interference in the determination of medium- and high-concentration creatinine. Dose-response experiments revealed that the interference effect of ethamsylate on the determination of creatinine at low, medium, and high concentrations was a cubic regression curve. In the samples with low, medium, and high concentrations of creatinine, the lowest effective doses of ethamsylate interfering with the sarcosine oxidase method were 5.78 mg/L, 6.36 mg/L, and 9.66 mg/L, respectively. The lowest effective doses of ethamsylate that interfered with the low-, medium-, and high-creatinine samples via the picric acid method were 70.16 mg/L, 617.36 mg/L, and 859.19 mg/L, respectively. The interference pattern analysis suggests that the degree of interference diminished as creatinine concentration increased.

Conclusions: Both the sarcosine oxidase method and the picric acid method are affected by ethamsylate. The picric acid method was relatively less effective and was effective mainly for creatinine samples at low concentrations.