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Reliability of Point-of-Care Vitamin D Testing for Use in Primary Health Care: A Comparative Evaluation with
Salma Younes1,2, Tasneem AlHamad1, Alma Al-Louzi1
1Biomedical Sciences Department, College of Health Sciences, Qatar University, Doha, Qatar.
Background:
Accurate measurement of serum 25-hydroxyvitamin D [25(OH)D] is essential for diagnosing deficiency and guiding treatment. While automated chemiluminescent immunoassays (CLIAs) are widely used in centralized laboratories, growing demand for rapid decisions has increased interest in reliable point-of-care (POC) testing. However, comparative data between modern POC systems and established laboratory analyzers remain limited.
Aim:
To assess the analytical agreement and diagnostic performance of a fluorescence-based POC vitamin D immunoassay and a contemporary automated CLIA platform against a benchmark automated CLIA system.
Methods:
A total of 311 human serum samples covering deficient, insufficient, sufficient, and high 25(OH)D concentrations were analyzed using one fluorescence-based POC assay and two automated CLIA platforms. Agreement was evaluated using Spearman correlation, Bland-Altman analysis, and receiver operating characteristic (ROC) curves. Diagnostic performance for vitamin D insufficiency (<30 ng/mL) was assessed by sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), overall percent agreement (OPA), and Cohen's κ.
Results:
All three assays showed excellent concordance, with strong correlations (r = 0.86-0.92) and similar median 25(OH)D concentrations. Bland-Altman analysis demonstrated modest, clinically acceptable biases (-14.3% to +10.0%) without proportional error. Diagnostic agreement was high, with AUC values of 0.96-0.98 and Cohen's κ values of 0.84-0.85, indicating high agreement in classifying vitamin D insufficiency. The fluorescence-based POC assay showed performance comparable to both automated CLIAs, with specificity of 91-96% and NPV of 91-97%.
Conclusion:
Both the fluorescence-based POC immunoassay and the contemporary automated CLIA platform demonstrated high diagnostic agreement with the benchmark automated CLIA system. These findings support the potential utility of both laboratory-based and decentralized assays for routine vitamin D screening in appropriate clinical settings.
