TABLE 3.
Sensitivity and specificity of the indirect immunofluorescence assay from company A used in commercial laboratories for detection of total immunoglobulinsa
| Cutoff | Sensitivity, % (95% CI) | Specificity, % (95% CI) | +LR (95% CI) | −LR (95% CI) |
|---|---|---|---|---|
| ≥0 | 100.00 (96.3–100.0) | 0.00 (0.0–2.0) | 1.00 (1.0–1.0) | |
| 40 | 70.10 (60.0–79.0) | 74.59 (67.7–80.7) | 2.76 (2.1–3.6) | 0.40 (0.3–0.5) |
| 80 | 64.95 (54.7–73.1) | 79.25 (70.3–86.5) | 3.10 (3.2–7.1) | 0.41 (0.3–0.5) |
| 160 | 63.92 (53.5–73.4) | 89.19 (83.8–93.3) | 5.91 (3.8–9.2) | 0.40 (0.3–0.5) |
| 320 | 55.67 (45.2–65.8) | 95.14 (91.0–97.8) | 11.44 (5.9–22.2) | 0.47 (0.4–0.6) |
| 640 | 50.52 (40.2–60.8) | 97.3 (93.8–99.1) | 18.69 (7.7–45.4) | 0.51 (0.4–0.6) |
| 1,280 | 43.30 (33.3–53.7) | 98.92 (96.1–99.9) | 40.05 (9.9–161.9) | 0.57 (0.5–0.7) |
| 2,560 | 27.84 (19.2–37.9) | 100.00 (98.0–100.0) | 72.47 (10.1–519.6) | 0.61 (0.5–0.7) |
| 10,240 | 27.84 (19.2–37.9) | 100.00 (98.0–100.0) | 0.72 (0.6–0.8) | |
| >10,240 | 0.00 (0.0–3.7) | 100.00 (98.0–100.0) | 1.00 (0.8–0.9) |
a
95% CI, 95% confidence interval; +LR, positive likelihood ratio; −LR, negative likelihood ratio. Values in boldface indicate that the results were obtained at a cutoff value of ≥1:40 for total immunoglobulin detection, which is the reference cutoff value for positivity.