TABLE 6.
Key performance characteristics of the NCEH's LC-MS/MS measurement procedure as of July 20091
| 25(OH)D3 | 25(OH)D2 | |
| Accuracy | ||
| Compared with SRM 9722 | +2 to + 83 | −18 to 303 |
| Recovery (mean ± SD) | 95 ± 3% | 97 ± 3% |
| Precision,4% | 6–85 | 6–96 |
| Sensitivity, nmol/L | <2.5 | <2.5 |
| Specificity | Yes7 | Yes |
The LC-MS/MS measurement procedure is in development. It has not yet been used to measure serum 25(OH)D in NHANES participants. When development is completed, the LC-MS/MS will be used to measure serum 25(OH)D in NHANES 2007 and later.
SRM 972 certificate values (15) compared with CDC data (12 replicates per level over 3 d) from assays performed in August to September 2008.
Values expressed as percent of SRM 972.
NCEH coefficient of variation data derived from 29 assays performed in September 2008 to July 2009.
The 25(OH)D3 concentrations ranged from 31 to 85 nmol/L. Unit conversion: 2.5 nmol/L = 1 ng/mL.
The 25(OH)D2 concentrations ranged from 2 to 22 nmol/L; precision for 7–22 nmol/L. Unit conversion: 2.5 nmol/L = 1 ng/mL.
Measurement procedure does not separate serum 25(OH)D3 from 3-epi-25(OH)D3.