Table 4.
Comparison of method performance for laboratories with continuous participation vs. laboratories with occasional participation in 4 consecutive VITAL-EQA rounds (rounds 26–29)1
| Continuous vs. occasional participation | Round | Analyte | |||||
|---|---|---|---|---|---|---|---|
| VIA | VID | FOL | B12 | FER | CRP2 | ||
| Acceptable performance for difference (%) | 26 | 63 vs. 0 | 32 vs. 27 | 67 vs. 61 | 87 vs. 80 | 96 vs. 100 | 71 vs. 100 |
| 27 | 63 vs. 17 | 42 vs. 53 | 50 vs. 44 | 80 vs. 100 | 89 vs. 83 | 63 vs. 90 | |
| 28 | 56 vs. 48 | 38 vs. 55 | 46 vs. 13 | 73 vs. 53 | 100 vs. 100 | 54 vs. 63 | |
| 29 | 50 vs. 67 | 38 vs. 67 | 50 vs. 27 | 53 vs. 67 | 93 vs. 72 | 65 vs. 53 | |
| Acceptable performance for imprecision (%) | 26 | 72 vs. 17 | 82 vs. 100 | 79 vs. 100 | 60 vs. 87 | 81 vs. 100 | 100 vs. 100 |
| 27 | 69 vs. 50 | 79 vs. 53 | 96 vs. 94 | 80 vs. 87 | 81 vs. 67 | 100 vs. 100 | |
| 28 | 81 vs. 85 | 71 vs. 58 | 88 vs. 67 | 80 vs. 69 | 89 vs. 73 | 100 vs. 100 | |
| 29 | 69 vs. 67 | 71 vs. 90 | 88 vs. 73 | 67 vs. 79 | 81 vs. 72 | 100 vs. 100 | |
| Laboratories (n) | 26 | 16 vs. 2 | 8 vs. 5 | 8 vs. 6 | 5 vs. 5 | 9 vs. 4 | 9 vs. 3 |
| 27 | 16 vs. 4 | 8 vs. 5 | 8 vs. 7 | 5 vs. 5 | 9 vs. 6 | 9 vs. 5 | |
| 28 | 16 vs. 9 | 8 vs. 11 | 8 vs. 5 | 5 vs. 12 | 9 vs. 11 | 9 vs. 9 | |
| 29 | 16 vs. 6 | 8 vs. 7 | 8 vs. 5 | 5 vs. 8 | 9 vs. 6 | 9 vs. 5 | |
| Methods (n) | |||||||
| HPLC | 26 | 15 vs. 2 | 3 vs. 0 | NA | NA | NA | NA |
| 27 | 15 vs. 3 | 3 vs. 0 | NA | NA | NA | NA | |
| 28 | 15 vs. 7 | 3 vs. 0 | NA | NA | NA | NA | |
| 29 | 15 vs. 5 | 3 vs. 0 | NA | NA | NA | NA | |
| IA/PB | 26 | 1 vs. 0 | 4 vs. 5 | 5 vs. 3 | 5 vs. 4 | 9 vs. 4 | 9 vs. 3 |
| 27 | 1 vs. 0 | 4 vs. 4 | 5 vs. 4 | 5 vs. 4 | 9 vs. 6 | 9 vs. 5 | |
| 28 | 1 vs. 0 | 4 vs. 5 | 5 vs. 4 | 5 vs. 9 | 9 vs. 10 | 9 vs. 9 | |
| 29 | 1 vs. 0 | 4 vs. 5 | 5 vs. 4 | 5 vs. 7 | 9 vs. 5 | 9 vs. 5 | |
| HPLC-MS/MS | 26 | NA | 1 vs. 0 | 1 vs. 0 | NA | NA | NA |
| 27 | 0 vs. 1 | 1 vs. 1 | 1 vs. 0 | NA | NA | NA | |
| 28 | 0 vs. 2 | 1 vs. 6 | 1 vs. 0 | NA | NA | NA | |
| 29 | 0 vs. 1 | 1 vs. 2 | 1 vs. 0 | NA | NA | NA | |
| MBA | 26 | NA | NA | 2 vs. 3 | 0 vs. 1 | NA | NA |
| 27 | NA | NA | 2 vs. 3 | 0 vs. 1 | NA | NA | |
| 28 | NA | NA | 2 vs. 1 | 0 vs. 2 | NA | NA | |
| 29 | NA | NA | 2 vs. 1 | NA | NA | NA | |
| Unknown (not reported) | 26 | NA | NA | NA | NA | NA | NA |
| 27 | NA | NA | NA | NA | NA | NA | |
| 28 | NA | NA | NA | 0 vs. 1 | 0 vs. 1 | NA | |
| 29 | NA | NA | NA | 0 vs. 1 | vs. 1 | NA | |
1
B12, serum vitamin B12; CRP, serum C-reactive protein; FER, serum ferritin; FOL, serum folate; IA/PB, immunoassay/protein binding assay; MBA, microbiologic assay; 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, the CDC assay limit of quantitation for these rounds.