The Role of Interferences in the Increasing Incidence of Vitamin D Deficiency

Objective: Lipemia is one of the causes of interference in immunoassay and LC-MS/MS methods. Increased prevalence of vitamin D deficiency in the US, where obesity is gradually increasing, raises the suspicion that high levels of fat diet and blood lipid levels interfere with vitamin D measurement results. The focus of this study was to investigate the effect of blood lipid profiles on vitamin D results and prevent the matrix effect. Material and Methods: In this study, 25OH vitamin D3 (25OHD3) levels of 100 samples consecutively accepted to biochemistry laboratory regardless of age and sex were measured by the LC-MS/MS method, and each sample was restudied after 1/10 dilution. After dilution restudy, two groups were obtained-group 1 (results deviating below 20%) and group 2 (results deviating above 20%)—and the difference between the groups was investigated. There were 79 patients in group 1 and 21 patients in group 2. In our study, lipid profiles (triglyceride, total cholesterol, HDL, LDL) from the same samples of consecutive vitamin D patients were studied. Results: It was observed that the triglyceride, total cholesterol HDL, LDL, and 25OHD3 measurements of group 1 and group 2 were similar (p > 0.05). While the mean vitamin D value in the second group was 9.94 ± 7.85, the mean vitamin D value after dilution was measured as 39.23 ± 18.13 and was statistically significant. 25OHD3 concentrations of 21 patients out of 100 were found to be falsely low. Measurements were repeated to confirm the results. Conclusion: The matrix effect caused by exogenous and endogenous interferences in the blood could be a hidden factor increasing the prevalence of vitamin D deficiency by causing falsely low 25OHD3 values. Suspicious results should be remeasured by a dilution study.