6725 CDC’s Efforts In Standardizing Of Vitamin D Tests: Challenges And Potential Patient Misclassifications

Abstract Disclosure: O. Sugahara: None. T. Buchannan: None. U. Danilenko: None. A. Ribera: None. L. Collins: None. F. Pokuah: None. A.N. Lyle: None. H.W. Vesper: None. Accurate and reliable tests are critical for the correct diagnosis and treatment of patients, correct interpretation of research data, and effective evidence-based clinical decision-making. CDC’s Clinical Standardization Programs (CDC CSP) assist with assessing and improving the analytical performance of biomarker tests, such as vitamin D, performed in patient care, public health, and research. CDC CSP established the Vitamin D Standardization-Certification Program (VDSCP) in 2013. The program has seen improvements in calibration bias since its inception. In 2022, mass spectrometry-based assays had a mean bias of 0.55% and immunoassays had a mean bias of 0.86%, for all assays enrolled in VDSCP. This indicates that overall, the assays enrolled in the VDSCP are well-calibrated. However, with improvements in calibration, sample-specific inaccurate results became more apparent. These observations can be explained by a lack of analytical specificity and cross-reactivity, as well as incomplete analyte recovery. For example, some mass spectrometry-based assays measure C3-epi-25-hydroxyvitamin D3 in addition to 25-hydroxyvitamin D3 causing falsely elevated results in some samples. Some immunoassays appear to show cross-reactivity with 24,25-dihydroxyvitamin D3 also causing falsely elevated vitamin D concentration. These inaccuracies may result in incorrect patient classification. Preliminary assessment of data reveals evidence that could lead to patient misclassification. According to the Endocrine Society’s guideline, a vitamin D level of 50 nmol/L or less is considered as deficiency and a vitamin D level of 50-75 nmol/L is considered as insufficiency. For example, a VDSCP sample with a vitamin D reference value of 55.1 nmol/L should be classified as insufficient in vitamin D. However, 44 % of results reported would classify this sample are deficient. Another sample with a vitamin D reference value of 45.4 nmol/L should be classified as deficient in vitamin D. However, 18 % of the results reported would classify this sample as insufficient. While most vitamin D tests are effective, it is important for healthcare providers to be aware of the potential inconsistencies associated with vitamin D tests to avoid misclassification of the patients. Presentation: 6/2/2024