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Background: Almost all the automated chemiluminescence analyzers in the market cannot detect total 25-hy-droxyvitamin D (25-OH VD) in fingertip blood sample due to the limited volume. This study aimed to develop a relatively simple pretreatment method to obtain plasma from the fingertip blood samples with limited volume and to establish and evaluate the performance of a chemiluminescence immunoassay (CLIA) for detecting 25-OH VD in plasma.
Methods: Fixed volume of plasma was obtained using a special glass capillary to pretreat the fingertip blood. The coated microwells were inserted and the reagents were dispensed into wells in the test strips which can be continuously tested on a small automated chemiluminescence analyzer. The performance of the developed method was evaluated, and the method comparison studies were conducted.
Results: The limit of detection (LOD) was 1.38 ng/mL. The intra-assay precision of the anticoagulant whole blood samples with low, medium, high concentrations of 25-OH VD were 5.45%, 8.20%, 4.97%, respectively. Different metabolic forms of vitamin D have different degrees of cross-interference with antibodies used in the developed method, especially the active metabolites. The cross reactivity (CR) values of 1,25-dihydroxyvitamin D2 (1,25-(OH)2 VD2) and 1,25-dihydroxyvitamin D3 (1,25-(OH)2 VD3) were 5.83% and 9.13%, respectively. The method comparison results of plasma from the venous blood samples showed that correlation coefficient (R2) is 0.94, with a slight positive bias of +1.1% [95% limits of agreement (± 1.96 SD); -25.8% to 28.1%]. Comparing the results detected by the developed method (plasma from fingertip blood samples) with Roche (plasma from anticoagulant venous blood), good linear relativity was noted, with a slight negative bias of -1.2% [95% limits of agreement (± 1.96 SD); -28.7% to 26.4%].
Conclusions: The developed pretreatment method for fingertip blood and the CLIA method can be used to assess the vitamin D status. The correlation of performance and method with the Roche test was good, and the whole test needs only 30 minutes. The developed method can fully satisfy very busy clinical labs.
DOI: 10.7754/Clin.Lab.2020.191034
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