CDC: Sample-specific inaccuracies persist for many vitamin D tests
Click Here to Manage Email Alerts
Key takeaways:
- Most vitamin D tests are well calibrated, according to the CDC.
- With improved calibration, sample-specific inaccurate results became more apparent.
BOSTON — Vitamin D test results have become more reliable during the past decade after quality improvement measures, but inaccuracies persist for some assays that can affect diagnosis and treatment decisions, researchers reported.
Vitamin D is among the most commonly requested laboratory tests, according to the CDC. 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, Otoe Sugahara, BS, a research chemist with the clinical reference laboratory at the CDC’s National Center for Environmental Health, said during a poster presentation at ENDO 2024. To assist with the standardization of vitamin D assays, CDC established a vitamin D standardization certification program in 2013.
“Although most vitamin D tests from participants in CDC’s Vitamin D Standardization-Certification Program have improved, there remains some inaccuracies specific to the serum sample,” Sugahara told Healio. “CDC is working with program participants to address these situations.”
The researchers reported that in 2022, mass spectrometry-based vitamin D assays had a mean bias of 0.55% and immunoassays had a mean bias of 0.86% for all assays enrolled in the program, indicating that, overall, enrolled assays are well calibrated.
“However, with improvements in calibration, sample-specific inaccurate results became more apparent,” the researchers wrote. The researchers attributed the inaccuracies to lack of analytical specificity and cross-reactivity, as well as incomplete analyte recovery.
As an example, CDC noted that some of the mass spectrometry-based assays measure C3-epimer of 25-hydroxyvitamin D3 in addition to 25-(OH)D3, causing falsely elevated results for some samples. Additionally, some immunoassays appear to show cross-reactivity with 24,25-dihydroxyvitamin D3, which can also cause falsely elevated vitamin D levels.
According to the Endocrine Society, a vitamin D level of 50 nmol/L or less is considered deficient and a level of 50 nmol/L to 75 nmol/L is considered insufficient. As Healio previously reported, the society is releasing an updated clinical practice guideline on vitamin D for the prevention of disease during ENDO 2024.
“Some inaccuracies appear to be caused by a lack of analytical specificity and other factors, such as analytical sensitivity,” Sugahara told Healio. “These inaccuracies can result in incorrect classification of patients’ vitamin D status.”
Sugahara noted that since 2013, assays enrolled in the program have generally improved and become better calibrated.
“However, with improved calibration, sample-specific inaccurate results became more apparent, which needs to be addressed,” Sugahara told Healio.
Reference:
CDC. Vitamin D Standardization-Certification Program. https://www.cdc.gov/clinical-standardization-programs/php/vitamin-d/index.html. Published April 24, 2024. Accessed June 2, 2024.
Collapse
Sugahara O, et al. SUN-272. Presented at: ENDO annual meeting; June 1-4, 2024; Boston.
Click Here to Manage Email Alerts