Table 3.
Descriptive statistics for aggregate difference from CDC target and imprecision for VITAL-EQA rounds 10–291
| Analyte | ||||||
|---|---|---|---|---|---|---|
| VIA | VID | FOL | B12 | FER | CRP2 | |
| Difference (%) | ||||||
| Minimal acceptable criteria | <±12.1 | <±14.8 | <±25.6 | <±16.4 | <±38.2 | <±34.6 |
| All points included | ||||||
| n | 1113 | 483 | 520 | 441 | 756 | 505 |
| Mean | −1.02 | 10.2 | −2.10 | 1.90 | −10.5 | 38.1 |
| Median | −2.20 | 3.27 | −6.85 | −1.90 | −9.45 | 6.90 |
| Q1 | −10.7 | −15.0 | −26.8 | −11.1 | −22.2 | −6.20 |
| Q3 | 6.3 | 21.2 | 8.90 | 10.9 | −0.28 | 33.5 |
| IQR | 17.0 | 36.2 | 35.7 | 22.0 | 21.9 | 39.7 |
| 5th | −30.6 | −50.4 | −58.2 | −36.5 | −49.9 | −42.7 |
| 95th | 26.2 | 78.8 | 81.8 | 42.8 | 19.2 | 199.9 |
| Lower 95% CI | −2.56 | 4.78 | −6.47 | −1.03 | −13.1 | 25.7 |
| Upper 95% CI | 0.51 | 15.6 | 2.26 | 4.84 | −7.85 | 50.5 |
| Far outliers removed | ||||||
| n | 1076 | 462 | 505 | 416 | 747 | 463 |
| Mean | −2.62 | 4.80 | −6.92 | 0.67 | −11.8 | 11.5 |
| Median | −2.30 | 3.07 | −7.60 | −2.00 | −9.40 | 4.90 |
| Q1 | −10.6 | −14.4 | −26.9 | −10.9 | −21.8 | −7.56 |
| Q3 | 5.60 | 19.2 | 8.20 | 9.38 | −0.4 | 24.8 |
| IQR | 16.2 | 33.6 | 35.1 | 20.3 | 21.4 | 32.3 |
| 5th | −28.4 | −45.4 | −58.0 | −25.0 | −48.8 | −42.3 |
| 95th | 22.5 | 57.2 | 44.9 | 34.7 | 15.7 | 85.9 |
| Lower 95% CI | −3.58 | 1.68 | −10.2 | −1.47 | −13.3 | 7.48 |
| Upper 95% CI | −1.65 | 7.92 | −3.65 | 2.80 | −10.4 | 15.5 |
| Imprecision (%CV) | ||||||
| Minimal acceptable criteria | <7.1 | <8.5 | <17.0 | <10.1 | <11.2 | <36.9 |
| All points included | ||||||
| n | 1110 | 490 | 520 | 441 | 756 | 505 |
| Mean | 5.60 | 8.20 | 8.98 | 6.66 | 6.50 | 8.17 |
| Median | 3.25 | 4.95 | 5.45 | 4.30 | 4.00 | 4.50 |
| Q1 | 1.90 | 2.90 | 3.50 | 2.20 | 2.30 | 2.40 |
| Q3 | 6.20 | 8.28 | 9.13 | 7.20 | 7.00 | 8.70 |
| IQR | 4.30 | 5.38 | 5.63 | 5.00 | 4.70 | 6.30 |
| 5th | 0.90 | 1.30 | 1.30 | 0.70 | 0.90 | 0.71 |
| 95th | 19.3 | 26.7 | 25.1 | 25.3 | 19.1 | 24.6 |
| Lower 95% CI | 5.18 | 7.17 | 7.51 | 5.90 | 5.80 | 7.08 |
| Upper 95% CI | 6.01 | 9.22 | 10.4 | 12.6 | 7.20 | 9.27 |
| Far outliers removed | ||||||
| n | 1051 | 473 | 498 | 422 | 718 | 477 |
| Mean | 4.40 | 7.19 | 6.88 | 5.49 | 4.94 | 5.72 |
| Median | 3.10 | 4.80 | 5.25 | 4.05 | 3.90 | 4.20 |
| Q1 | 1.80 | 2.90 | 3.33 | 2.20 | 2.20 | 2.25 |
| Q3 | 5.60 | 7.90 | 8.40 | 6.48 | 6.30 | 7.70 |
| IQR | 3.80 | 5.00 | 5.08 | 4.28 | 4.10 | 5.45 |
| 5th | 0.90 | 1.27 | 1.30 | 0.70 | 0.90 | 0.58 |
| 95th | 12.3 | 20.7 | 16.8 | 14.5 | 13.4 | 15.6 |
| Lower 95% CI | 4.16 | 6.31 | 6.37 | 4.95 | 4.64 | 5.28 |
| Upper 95% CI | 4.65 | 8.07 | 7.38 | 10.2 | 5.24 | 6.16 |
1
B12, serum vitamin B12; CRP, serum C-reactive protein; FER, serum ferritin; FOL, serum folate; VIA, serum vitamin A; VID, serum 25-hydroxyvitamin D; VITAL-EQA, Vitamin A Laboratory-External Quality Assessment.
2
CRP pools featured are those with concentrations ≥0.9 mg/L (limit of quantitation) as measured by the CDC assays; this CRP limit of quantitation (3 × limit of detection) was used for the majority of rounds (16 out of 20 rounds, 88% of the pools); CRP limit of quantitation was 9 mg/L for round 10, 1.3 mg/L for rounds 11–13, and 0.9 mg/L for rounds 14–29.