To assess the interference by calcium dobesilatein 7 peroxidase-baseduric acid assays and to determine its clinical significance.

In the in vitro experiments, uric acid in pooled serum with final concentrations of calcium dobesilate additions (0, 2, 4, 8, 16, 32, and 64 μg/ml)were measured by 7 peroxidase-based assays. Percent Bias (%) was calculated relative to the drug-free specimen. In the in vivo experiments, changes in serum uric acid and calcium dobesilate concentrations were observed before and after calcium dobesilate administration (baseline, 0 h, 1 h, 2 h, 3 h, 4 h, 6 h) involunteers. The interference in different assays was assessed compared with LC-IDMS/MS method. Calcium dobesilate levels in 40 specimens from those taking calcium dobesilate were measured by HPLC method.Of the 40 specimens, 10 were selected to analyse the levels of uric acid by both peroxidase and UV measurement method to assess the impact in clinical status.

In the in vitro study, concentrations of uric acid measured by 7 peroxidase-based assays were reduced by -6.3% to -21.2% compared with drug-free serum, when theconcentration of calcium dobesilate was16 μg/ml. In the in vivo study, comparedto UA levels at 0 h, the biasesof serum uric acid determined by peroxidase method after calcium dobesilate administration(1 h, 2 h, 3 h, 4 h, 6 h) were of -3.33%, -6.79%, -7.49%, -6.07%, -4.09%, respectively. The observed uric acid concentrations for 8 participants measured by enzymatic assays were inhibited by -3.75% to -6.89% at 0 hour and by -16.9% to-22.22% at 2 hours relative to the concentrations measured by the LC-IDMS/MS method.

Calcium dobesilate produced a clinically significant negative interference with uric acid in all peroxidase-based uric acid assays, which may result in false evaluation of uric acid level in clinical status. Significant differences in the degree of interference were observed among the assays. (Chin J Lab Med, 2015, 38: 600-604)

Uric acid; Calcium dobesilate; Urate oxidase; Peroxidase; Colorimetry