Objective:

To evaluate the accuracy of a smartphone-based joint self-assessment app in measuring active rheumatoid arthritis compared to physician assessments.

Approach:

Key Findings:

• The app overestimated active disease compared to physician assessments.
• Patient-reported joint counts showed a 95% positive predictive value (PPV) for low disease activity but only a 50% negative predictive value (NPV) for active disease, indicating limited reliability in detecting active disease.
• Agreement between patient and physician assessments was modest, with correlation coefficients of 0.5 for tender joints and 0.33 for swollen joints.
• Patients reported higher counts of tender and swollen joints than physicians, particularly for swollen joints.

Interpretation:

Patient-derived joint counts may be useful for confirming low disease activity or remission but are less reliable for identifying active disease.

Limitations:

• Modest agreement may reflect real-world differences in patient environments and timing.
• Difficulty in distinguishing pain from tenderness may affect reporting accuracy.
• Comorbid conditions like fibromyalgia may influence patient-reported counts.
• Limitations of app-based training without in-person or video instruction should be noted.

Conclusion:

While the app shows potential for confirming low disease activity, it is not reliable for accurately assessing disease activity in less well-controlled rheumatoid arthritis, highlighting the need for caution in its use.

Sources:

• ACR Open Rheumatology
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