Date Published: February 12, 2018
Publisher: Public Library of Science
Author(s): Xiuzhi Guo, Li’an Hou, Yicong Yin, Jie Wu, Fang Zhao, Liangyu Xia, Xinqi Cheng, Qian Liu, Li Liu, Ermu Xu, Ling Qiu, Hilda Luna-Záizar.
Previously, we reported the strong negative interference of calcium dobesilate, a vasoprotective agent, in creatinine assays involving the Trinder reaction. It is hypothesized that a similar effect occurs in the detection of uric acid (UA), total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C). The interferences of calcium dobesilate during the detection of the five serum analytes were investigated on automated systems/analysers, and the effects were compared among eight different assay systems for each analyte. A calcium dobesilate standard was added into two sets of the blank serum pools of each analyte at final concentrations of 0, 2, 4, 8, 16, 32, and 64 μg/mL. The percentage deviation of each analyte value was calculated between each drug concentration and the drug-free samples. The clinically acceptable error levels for UA, TC, TG, HDL-C, and LDL-C were defined as ±4.87%, ±4.1%, ±9.57%, ±5.61%, and ±5.46%, respectively. The observed interference was concentration dependent for each analyte. In the presence of 16 μg/mL calcium dobesilate, which was within the therapeutic range, all seven Trinder reaction-based UA assay systems, two TG assay systems, two HDL-C assay systems and one TC assay system exhibited negative drug interferences. Calcium dobesilate negatively interferes with the detection of UA, TG, TC, and HDL-C in assay systems based on the Trinder reaction. The effect was most significant in UA and TG detection.
The Trinder reaction is a fundamental process employed in a variety of clinical biochemical tests. Currently, Trinder-coupled chromogenic reactions are used for the determination of creatinine (Cr), uric acid (UA), cholesterol, and triglycerides (TG). Originally, phenol was used as the chromogenic agent for the Trinder reaction. With the application of a number of alternative chromogenic materials, such as 2,4-dichlorophenol, the sensitivity of this method has been improved significantly. However, due to the poor substrate specificity of catalytic peroxidase for the Trinder reaction, multiple substances, such as ascorbic acid [1,2], etamsylate , N-acetylcysteine , and bilirubin , can interfere with the assay’s results. Recently, we confirmed that the medication calcium dobesilate produces significant negative interferences with the determination of creatinine using sarcosine oxidase-based assays, and the extent of interference differs significantly among the different assay systems .
Considering the clinically acceptable deviation of ±4.87% for UA, the exogenous addition of calcium dobesilate clearly exhibited dose-dependent negative interference with the determination of UA in all seven Trinder reaction-based assays (Fig 1). In the presence of 16 μg/mL calcium dobesilate, all seven Trinder reaction-based UA assays exhibited deviations ranging from -6.3% to -21.2% in the low UA serum group (Fig 1A). Furthermore, six of the seven Trinder reaction-based UA assays (except for the Maker assay), exceeded the acceptable limits of deviations for the UA (-4.87%) in the high UA serum group, with deviations ranging from -5.7% to -9.6% (Fig 1B). The same calcium dobesilate concentrations produced significantly different levels of interference among the different assays, with the Ortho/Vitros assay exhibiting the maximum interference and the Maker assay exhibiting the minimum interference. As a control assay, the Siemens system using the UA-UV method did not show any interference (Fig 1).
This study investigated the interferences of calcium dobesilate in the detection of the five serum analytes. The observed degree of interference is related to the drug concentration in the serum. In our previous study , calcium dobesilate was administered to ten volunteers for three days, and the trough and peak serum concentrations were found to be 2.66–8.33 μg/mL and 12.83–23.15 μg/mL, respectively. This study reveals that at a plasma concentration as low as 4 μg/mL, calcium dobesilate can negatively interfere with the measurement of UA in the Ortho/Vitros assay. At a concentration of 16 μg/mL, calcium dobesilate negatively interferes in seven assays for UA, two assays for TG, two assays for HDL-C, and one assay for TC. Importantly, these effects were observed to be dose-dependent; the higher the dosage, the higher the interference. Therefore, the administration of calcium dobesilate in patients will result in sufficiently high serum concentrations of calcium dobesilate to artificially lower the values of the serum analytes, and the interference will be greater if blood samples are collected shortly after a dose. Because calcium dobesilate is primarily excreted through the kidneys, drug accumulation can occur in patients with impaired kidney function, resulting in even more severe interference in the testing results. It has been reported previously that the calcium dobesilate concentration in patients taking calcium dobesilate can be as high as 63.35 μg/mL . The interference is expected to be more substantial at such concentration levels.
In this study, we confirmed through in vitro addition experiments that calcium dobesilate negatively interferes with the detection of UA, TC, TG, and HDL-C in assay systems based on the Trinder reaction. The effect is most significant in UA and TG and varies among assay systems from different suppliers. Consequently, physicians should practise prudent judgement regarding the reported levels of creatinine, UA, TC, TG, and HDL-C in patients taking calcium dobesilate.