The effect of calcium dobesilate on creatinine measurement by sarcosine oxidase assay

Objective To investigate the interference effect of calcium dobesilate on serum creatinine levels by Sarcosine oxidase-based assay. Methods 1.Interference test in vivo: Ten patients with chronic renal diseases from Huangshi second hosptial were recruited.Serum creatinine (sarcosine oxidase method,Scr1; deiminase method,Scr2),urea,and cystatin C were detected and compared before and after one week administration of calcium dobesilate; 2.Interference test in vitro:to detect whether 100 mg/L calcium dobesilate has any interference with Scr1 and Scr2; 3.Dose-dependent interference test:To detect the interference effect of different concentrations of calcium dobesilate (1.25-20.0 mg/L) on different creatinine concentrations (404.5μmol/L or 65.9μmol/L) measured by sarcosine oxidase assay.Bias within 3.5% or 6.63μmol/L of creatinine levels was clinically acceptable.Statistical comparisons were made using Wilcoxon rank-sum test. Results There was significant difference of sarcosine oxidase-based serum creatinine levels between before and after one week administration of calcium dobesilate (P 0.05).Interference test showed that 95% confidence interval of interventional value (Dobs) of calcium dobesilate (100 mg/L) was (-173.9±2.86) μmol/L for the sarcosine oxidase assay and (1.21±3.14) μmol/L for deiminase method,indicating that calcium dobesilate caused a significant negative effect on the former enzymatic assay but not the latter one.In the dose effect interference test of calcium dobesilate,the regression equations were:Y=-2.7649X-0.0782 (R2=0.998,F=7943.4,P=0.000) for high creatinine levels and Y=0.0263X2-1.6394X-0.2754 (R2=0.996,F=2546.7,P=0.000) for low creatinine levels.The interference effect was less than the predetermined dmaxwith the calcium dobesilate concentrations of 4.4 mg/L in high concentration specimen and 3.5 mg/L in low concentration specimen. Conclusions Calcium dobesilate has a significant negative interference with serum creatinine detected by the sarcosine oxidase method,which leads to the bias of creatinine in patients with renal insufficiency. Hence, sarcosine-oxidase-based creatinine levels should be cautious when calcium dobesilate was used,and further check with another assay is necessary if possible.(Chin J Lab Med,2013,36:161-164) Key words: Calcium dobesilate; Sarcosine oxidase; Creatinine