Calcium dobesilate: A drug treatment for diabetic retinopathy can negatively interfere with the measurement of glycated albumin using the enzymatic method

A new method for anti-negative interference of calcium dobesilate in serum creatinine enzymatic analysis

Background

Serum creatinine is a widely used biomarker for evaluating renal function. Sarcosine oxidase enzymatic (SOE) analysis is currently the most widely used method for the detection of creatinine. This method was negatively interfered with by calcium dobesilate, causing pseudo‐reduced results. The aim of this study was to explore a new method to alleviate the negative interference of this drug on creatinine detection.

Method

We formulated eight drug concentrations and 12 creatinine concentrations from serum. The SOE method, the new method, and the Jaffe method were used for detection in five systems. Creatinine biases were analyzed under the conditions with or without the interference of calcium dobesilate, at consistent or inconsistent creatinine concentrations. Creatinine concentrations were also analyzed at three medical decision levels (MDLs).

Results

Calcium dobesilate had negative interference in creatinine SOE analysis. With the increase in calcium dobesilate concentrations, the negative bias increases. The new BG method showed an anti‐negative interference effect. In the Roche system, the BG method reduced the negative bias from −71.11% to −16.7%. In the Abbott system, bias was reduced from −45.15% to −2.74%. In the Beckman system, the bias was reduced from −65.36% to −7.58%. In the Siemens system, the bias was reduced from −58.62% to −7.58%. In the Mindray system, the bias was reduced from −36.29% to −6.84%.

Conclusion

The new method alleviated the negative interference of calcium dobesilate in creatinine SOE detection. The negative bias could be reduced from −60% or −70% to less than −20%.

Mechanisms of interference of p-diphenols with the Trinder reaction

p-Diphenols, such as homogentisic acid, gentisic acid, etamsylate, and calcium dobesilate, interfere with diagnostic tests utilizing the Trinder reaction but the mechanisms of these effects are not fully understood. We observed substantial differences both in oxidation of p-diphenols by horseradish peroxidase and their influence on oxidation of 4-aminoantipyrine and various phenolic substrates. Homogentisic acid was rapidly oxidized by the enzyme and completely blocked chromophore formation. Enzymatic oxidation of the remaining p-diphenols was slow and they only moderately inhibited chromophore formation. However, in the presence of standard substrates all tested p-diphenols were rapidly converted to p-quinones. Hydrogen peroxide consumption was significantly accelerated by homogentisic acid but not much affected by the other p-diphenols. The magnitude and mechanisms of interference caused by p-diphenols therefore depend on their structure which determines their electrochemical properties - while for homogentisic acid with an electron-donating substituent and a lower reduction potential both enzymatic oxidation and reduction of the peroxidase-generated radicals occur, for p-diphenols with electron-withdrawing substituents and higher reduction potentials only the second mechanism is significant. Correlation of the effects on the Trinder reaction with reduction potentials of interfering compounds allows prediction of such properties for a wide range of other reducing compounds based on this parameter. It also explains why compounds with very different structures but strong reducing properties show such effects.