Sensitivity, specificity, PPV, and NPV of different US and dermoscopic features for early PsA versus early seronegative and seropositive RA.
| Variables | Sensitivity (95% CI) | Specificity (95% CI) | PPV (95% CI) | NPV (95% CI) |
|---|---|---|---|---|
| US | ||||
| PTI pattern at MCP joint | 36.0% (18.0–57.5) | 95.2% (83.4–99.4) | 81.8% (51.4–95.0) | 71.4% (64.9–77.2) |
| CSE pattern at PIP joint | 20.0% (6.8–40.7) | 100% (91.6–100) | 100% (47.8–100) | 67.7% (63.3–71.8) |
| STE-FT of the digit | 40.0% (21.1–61.3) | 90.5% (77.4–97.3) | 71.4% (46.7–87.7) | 71.7% (64.5–78.0) |
| At least 1 of the abovementioned US features | 68.0% (46.5–85.0) | 88.1% (74.4–96.0) | 77.3% (58.9–89.0) | 82.2% (72.1–89.2) |
| Dermoscopy | ||||
| Dotted vessels of proximal nailfold | 96.0% (79.7–99.9) | 83.3% (68.6–93.0) | 77.4% (63.4–87.1) | 97.2% (83.6–99.6) |
| US + dermoscopy | ||||
| At least 1 US feature + dotted vessels of proximal nailfold on dermoscopy | 68.0% (46.5–85.0) | 90.5% (77.4–97.3) | 81.0% (61.7–91.8) | 82.6% (72.7–89.5) |
PPV: positive predictive value; NPV: negative predictive value; US: ultrasonography; PsA: psoriatic arthritis; RA: rheumatoid arthritis; PTI: peritendon inflammation of the extensor digitorum tendon; MCP: metacarpophalangeal; CSE: central slip enthesitis; PIP: proximal interphalangeal; STE-FT: soft tissue edema around flexor tendon.