Table 2.
ROC curve statistics showing sensitivity, specificity, +LR/−LR for one, two, or three AAPA reactivities in different scenarios (eRA versus healthy controls, estRA versus healthy controls, eRA versus SpA, eRA versus OIRD (namely SLE, pSS, myositis, GPA), RF/ACPA negative eRA versus healthy, RF/ACPA negative eRA versus SpA, RF/ACPA negative eRA versus OIRD), including AUC values.
| Early RA versus healthy | AUC 0.722 (95% CI: 0.658–0.780) | |||||||
|---|---|---|---|---|---|---|---|---|
| Number of AAPA | Sensitivity | 95% CI | Specificity | 95% CI | +LR | 95% CI | −LR | 95% CI |
| ⩾1 | 60 | 50.7–68.8 | 77.8 | 68.3–85.5 | 2.7 | 1.8–4.0 | 0.51 | 0.4–0.7 |
| ⩾2 | 36. 7 | 28.1–45.9 | 97.0 | 91.4–99.4 | 12.1 | 3.9–37.8 | 0.65 | 0.6–0.8 |
| 3 | 10 | 5.3–16.8 | 100 | 96.3–100.0 | 0.9 | 0.8–1.0 | ||
| Established RA versus healthy | AUC: 0.778 (95% CI: 0.726–0.824) | |||||||
| Number of AAPA | Sensitivity | 95% CI | Specificity | 95% CI | +LR | 95% CI | −LR | 95% CI |
| ⩾1 | 68.7 | 61.7–75.2 | 77.8 | 68.3–85.5 | 3.1 | 2.1–4.5 | 0.4 | 0.3–0.5 |
| ⩾2 | 47.7 | 40.5–54.9 | 97.0 | 91.4–99.4 | 15.7 | 5.1–48.4 | 0.54 | 0.5–0.6 |
| 3 | 21.5 | 16.0–28.0 | 100 | 96.3–100.0 | 0.78 | 0.7–0.8 | ||
| Early RA versus SpA | AUC: 0.751 (95% CI: 0.679–0.814) | |||||||
| Number of AAPA | Sensitivity | 95% CI | Specificity | 95% CI | +LR | 95% CI | −LR | 95% CI |
| ⩾1 | 60.00 | 50.7–68.8 | 86.00 | 73.3–94.2 | 4.3 | 2.1–8.7 | 0.47 | 0.4–0.6 |
| ⩾2 | 36.67 | 28.1–45.9 | 98.00 | 89.4–99.9 | 18.3 | 2.6–129.4 | 0.65 | 0.6–0.7 |
| 3 | 10.00 | 5.3–16.8 | 100.00 | 92.9–100.0 | 0.90 | 0.8–1.0 | ||
| Early RA versus OIRD | AUC 0.713 (95% CI: 0.657–0.765) | |||||||
| Number of AAPA | Sensitivity | 95% CI | Specificity | 95% CI | +LR | 95% CI | −LR | 95% CI |
| ⩾1 | 60.00 | 50.7–68.8 | 78.3 | 71.3–84.3 | 2.8 | 2.0–3.8 | 0.51 | 0.4–0.6 |
| ⩾2 | 36.67 | 28.1–45.9 | 92.8 | 87.7–96.2 | 5.07 | 2.8–9.2 | 0.68 | 0.6–0.8 |
| 3 | 10.00 | 5.3–16.8 | 100.00 | 97.8–100.0 | 0.90 | 0.8–1.0 | ||
| E. RF/ACPA neg early RA versus healthy | AUC: 0.599 (95% CI: 0.511–0.678) | |||||||
| Number of AAPA | Sensitivity | 95% CI | Specificity | 95% CI | +LR | 95% CI | −LR | 95% CI |
| ⩾1 | 40.82 | 27.0–55.8 | 77.8 | 68.3–85.5 | 1.8 | 1.1–3.0 | 0.76 | 0.6–1.0 |
| ⩾2 | 10.2 | 3.4–22.2 | 97.0 | 91.4–99.4 | 3.4 | 0.8–13.5 | 0.93 | 0.8–1.0 |
| 3 | 4.08 | 0.5–14.0 | 100 | 96.3–100.0 | 0.96 | 0.9–1.0 | ||
| RF/ACPA neg early RA versus SpA | AUC: 0.629 (95% CI: 0.528–0.723) | |||||||
| Number of AAPA | Sensitivity | 95% CI | Specificity | 95% CI | +LR | 95% CI | −LR | 95% CI |
| ⩾1 | 39.22 | 25.8–53.9 | 86.00 | 73.3–94.2 | 2.80 | 1.3–6.0 | 0.71 | 0.6–0.9 |
| ⩾2 | 9.80 | 3.3–21.4 | 98.00 | 89.4–99.9 | 4.90 | 0.6–40.5 | 0.92 | 0.8–1.0 |
| 3 | 3.92 | 0.5–13.5 | 100.00 | 92.9–100.0 | 0.96 | 0.9–1.0 | ||
| RF/ACPA neg early RA versus OIRD | AUC: 0.586 (95% CI: 0.517–0.652) | |||||||
| Number of AAPA | Sensitivity | 95% CI | Specificity | 95% CI | +LR | 95% CI | −LR | 95% CI |
| ⩾1 | 30.6 | 25.8–53.9 | 78.31 | 71.3–84.3 | 1.81 | 1.2–2.8 | 0.78 | 0.6–1.0 |
| ⩾2 | 6.1 | 3.3–21.4 | 92.77 | 87.7–96.2 | 1.36 | 0.5–3.7 | 0.97 | 0.9–1.1 |
| 3 | 4.1 | 0.5–13.5 | 100.00 | 97.8–100.0 | 0.96 | 0.9–1.0 | ||
AAPA, anti-acetylated peptide antibodies; ACPA, anti-citrullinated-peptide antibodies; AUC, area under the curve; CI, confidence interval; eRA, early RA; estRA, established RA; GPA, granulomatosis with polyangiitis; HC, healthy controls; +LR, positive likelihood ratio; –LR, negative likelihood ratio; OIRD, other inflammatory rheumatic diseases; pSS, primary Sjögren’s syndrome; RA, rheumatoid arthritis; RF, rheumatoid factor; ROC, receiver operating curves; SLE, systemic lupus erythematosus; SpA, spondyloarthritis