Table 1.
Characteristics of the commercial (A–H) and in house assays for PR3-ANCA
| Kit | Units | Number of standards | Dynamic range | Sample dilution | Data reduction | Assay performance | ||
| Sample | Intra-assay CV% | Interassay CV% | ||||||
| A | Units | Low pos | 1/101 | (OD samples/OD low positive) ×ELISA low positive | Negative | 3 | 4 | |
| Low | 2 | 9 | ||||||
| High | 3 | 2 | ||||||
| B | U/ml | 6 | 0–100 | 1/100 | Log/linear 4 parameter | 1 | 4.7 | 6.2 |
| 2 | 2.8 | 8.8 | ||||||
| 3 | 2.8 | 3.9 | ||||||
| C | U/ml | 7 | 0–100 | 1/51 | Best fit curve | 1 | 6.3 | 7.3 |
| 2 | 6.8 | 9.6 | ||||||
| D | Units | 5 | 24–305 | 1/40 | Linear best fit curve | – | – | – |
| E | U/ml | 6 | 0–100 | 1/101 | Linear plot of normalised OD: OD mean/OD max standard % | 1 | 13.3 | 7.6 |
| 2 | 12.1 | 5.6 | ||||||
| 3 | 13.9 | 5.3 | ||||||
| F | EU/ml | 4 | 21–170 | 1/101 | Linear/linear best fit curve | 1 | 10.6 | 8.4 |
| 2 | 6.5 | 8.7 | ||||||
| G | EU | 4 | 10–300 | 1/50 | Linear/linear | Low | 10 | 14.7 |
| Medium | 2.1 | 8 | ||||||
| High | 12.4 | 11.9 | ||||||
| Negative | 0 | 0 | ||||||
| H | AU/ml | 5 | 5–100 | 1/50 | Log/linear | Low | 8.1 | 9 |
| Medium | 4.7 | 5.2 | ||||||
| High | 2.6 | 5.7 | ||||||
| I/H | U/ml | 8 | 0–100 | 1/50 | Log/linear 4 parameter | Low | 5 | 7 |
| High | 21 | 24 | ||||||
CV, coefficient of variation; I/H, in house; OD, optical density; PR3-ANCA, proteinase 3 antineutrophil cytoplasmic antibodies.