Table 1.
Descriptive statistics and estimates of within-subject variability and agreement between serum concentrations of 25(OH)D measured at three time points (Baseline, +1yr, and +5yr) over a five-year period
| Analysis | All Subjects | |
|---|---|---|
| N | Values | |
| Season of blood draw* | ||
| January-March | 7 | |
| April-June | 6 | |
| July-September | 11 | |
| October-December | 5 | |
| Summary of 25(OH)D measures at: | ||
| Baseline | ||
| Mean (SD) | 28 | 60.0 (14.6) nmol/L |
| Median | 28 | 60.2 nmol/L |
| Range | 28 | 33.7-99.6 nmol/L |
| +1 Year | ||
| Mean (SD) | 29 | 59.8 (15.9) nmol/L |
| Median | 29 | 59.5 nmol/L |
| Range | 29 | 28.6-94.2 nmol/L |
| +5 Years | ||
| Mean (SD) | 26 | 56.6 (16.2) nmol/L |
| Median | 26 | 55.1 nmol/L |
| Range | 26 | 24.1-98.2 nmol/L |
| Measures of agreement | ||
| CV (95% CI) | 29 | 14.9% (12.4%-18.1%) |
| ICC (95% CI) | 29 | 0.71 (0.63-0.88) |
| Spearman rank correlation coefficients (95% CI) | ||
| Baseline vs. +1yr | 28 | 0.65 (0.37-0.82) |
| +1yr vs. +5yr | 26 | 0.61 (0.29-0.81) |
| Baseline vs. +5yr | 25 | 0.53 (0.17-0.77) |
| Baseline/+1yr average vs. +5yr | 25 | 0.65 (0.34-0.83) |
*
All participants had the serial blood draws during the same calendar month in each year. On average, samples were collected within a 13-day window (range 2-26 days).