CDC Vitamin D Standardization Certification Program

Program: Abstracts - Orals, Featured Poster Presentations, and Posters
Session: SUN 257-280-Disorders of Vitamin D Metabolism & Action
Sunday, June 16, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SUN-277
Yasamin Ebrahimi Rahmani*, Julianne Cook Botelho and Hubert W Vesper
Centers for Disease Control and Prevention, Atlanta, GA
Vitamin D has long been known for the role it plays in maintaining healthy bones. Recent research suggests that vitamin D deficiency may be associated with other chronic diseases such as cancer, diabetes, and cardiovascular disease. A patient's vitamin D level is commonly determined by measuring the circulating metabolites 25-hydroxyvitamin D2 and 25-hydroxyvitamin D3 and report the sum of these analytes as total 25-hydroxyvitamin D (25OHD). Vitamin D measurements need to be accurate and reliable to correctly diagnose a patient as being deficient. However, recent studies have cited significant variability in measurement results. For example, the Institute of Medicine has acknowledged that an individual may be deemed deficient depending on the laboratory where the sample is tested. This variability can lead to misdiagnosis of patients, inconsistency in clinical trial outcomes, and misinterpretation of population data for public health policy making. To minimize these problems, clinical vitamin D measurements need to be standardized.

CDC is addressing this need with its Vitamin D Standardization Certification Program, which is open to all laboratories and manufactures interested in achieving accurate and reliable vitamin D measurements. The Vitamin D Standardization Certification Program launched in November 2012 and is similar to the successful CDC Hormone Standardization Program (HoSt) for testosterone and estradiol. Standardization of total 25OHD in serum will be established through method comparison and bias estimation between a reference laboratory and the testing laboratory. The serum material used for this program are non-pooled, single-donor sera prepared following a standard protocol developed by the Clinical Laboratory and Standards Institute (CLSI) shown to contain minimal matrix effects and to behave similar to routine patient samples.

The program consists of two phases: Phase 1 is the calibration phase and Phase 2 is the verification/certification phase. In Phase 1, participants will receive a panel of 40 serum samples with assigned reference values to verify the accuracy and precision of their assay and adjust calibration if necessary. In Phase 2, the established calibration is verified with 10 blinded samples every quarter over a period of one year. Method comparison and bias estimation will be performed by the procedures described in CLSI EP9-A2 "Method Comparison and Bias Estimation Using Patient Samples." A laboratory is considered standardized and will receive certification when the observed bias and imprecision are within the predefined limits of +/-5.0% and ≤10.0%, respectively, after four consecutive challenges. Currently there are 15 participants enrolled in various stages of the program, including clinical laboratories, academic institutes, and immunoassay manufactures.

Nothing to Disclose: YER, JCB, HWV

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