Interpretation threshold values for patient-reported outcomes in patients participating in a digitally delivered first-line treatment program for hip or knee osteoarthritis

Objective
Establish proportions of patients reporting important improvement, acceptable symptoms and treatment failure and define interpretation threshold values for pain, patient-reported function and quality-of-life after participating in digital first-line treatment including education and exercise for hip and knee osteoarthritis (OA).

Methods
Observational study. Responses to the pain Numeric Rating Scale (NRS, 0-10 best to worst), Knee injury and Osteoarthritis Outcome Score 12 (KOOS-12) and Hip disability and Osteoarthritis Outcome Score 12 (HOOS-12, both 0-100 worst to best) were obtained for 4383 (2987) and 20341 (1264) participants with knee (hip) OA at 3 and 12 months post intervention.. Threshold values for Minimal Important Change (MIC), Patient Acceptable Symptom State (PASS) and Treatment Failure (TF) were estimated using anchor-based predictive modeling.

Results
70–85% reported an important improvement in pain, function and quality of life after 3 and 12 months follow-up. 42% (3 months) and 51% (12 months) considered their current state as satisfactory, whereas 2-4% considered treatment failed. MIC values were -1 (NRS) and 0-4 (KOOS/HOOS-12) across follow-ups and joint affected. PASS threshold value for NRS was 3, and 53–73 for the KOOS/HOOS-12 subscales Corresponding values for TF were 5 (NRS) and 34–55 (KOOS/HOOS-12). Patients with more severe pain at baseline had higher MIC scores and accepted poorer outcomes at follow-ups.

Conclusion
Threshold estimates aid in the interpretation of outcomes after first-line OA interventions assessed with NRS Pain and KOOS/HOOS-12. Baseline pain severity is important to consider when interpreting threshold values after first-line interventions in these patients.