American College of Rheumatology (ACR) and modified immunological criterion ACR performance. Data in parentheses are 95% CI.
| Immunological Criterion | SN | SP | PPV | NPV | LR+ | LR− |
|---|---|---|---|---|---|---|
| RF + ANA ≥ 1:320 | 56.9 (44–69.1) | 93.9 (88.8–97.2) | 80.4 (66–90.6) | 83.3 (76.8–88.6) | 9.4 (4.8–18.3) | 0.46 (0.35–0.61) |
| RF + AFA-IgA | 61.5 (48.6–73.3) | 88.5 (82.3–93.2) | 70.1 (56.6–81.5) | 84.0 (77.4–89.4) | 5.3 (3.3–8.7) | 0.43 (0.32–0.59) |
| AFA-IgA + ANA ≥ 1:320 | 64.6 (51.7–76.8) | 85.9 (79.2–91.0) | 66.6 (53.6–78.0) | 84.7 (78.0–90.0) | 4.5 (2.9–7.0) | 0.41 (0.29–0.56) |
| RF | 66.15 (53.3–77.4) | 87.2 (80.8–92.1) | 69.2 (56.3–80.4) | 85.53 (78.9–80.4) | 5.19 (3.29–8.17) | 0.39 (0.27–0.55) |
| Two out of three of RF, ANA ≥ 1:320, or AFA-IgA | 70.7 (58.1–81.4) | 78.5 (71.0–84.8) | 58.9 (47.2–69.9) | 86.0 (78.0–91.3) | 3.3 (2.3–4.6) | 0.37 (0.25–0.55) |
SN: sensitivity; SP: specificity; PPV: positive predictive value; NPV: negative PV; LR: likelihood ratio; RF: rheumatoid factor; ANA: antinuclear antibodies; AFA: anti-α-fodrin antibodies.