Objective: In order to facilitate data pooling between studies, we explored
harmonisation of patient-reported outcome measures (PROMS) in people with knee
pain due to osteoarthritis or knee trauma, using the Patient Acceptable Symptom State
scores (PASS) as a criterion.
Methods: We undertook a systematic literature review (SLR) of PASS scores, and
performed individual participant data (IPD) analysis of score distributions from
concurrently completed PROM pairs. Numerical rating scales (NRS), visual analogue
scales, KOOS and WOMAC pain questionnaires were standardised to 0 to 100 (worst)
scales. Meta-regression explored associations of PASS. Bland Altman plots compared
PROM scores within individuals using IPD from WebEx, KICK, MenTOR and NEKO
studies.
Results: SLR identified 18 studies reporting PASS in people with knee pain. Pooled
standardised PASS was 27 (95%CI: 21 to 35; n=6339). PASS was statistically similar
for each standardised PROM. Lower PASS was associated with lower baseline pain
(β=0.49, p=0.01) and longer time from treatment initiation (Q=6.35, p=0.04). PASS
scores were lowest in ligament rupture (12, 95%CI: 11 to 13), but similar between knee
osteoarthritis (31, 95%CI: 26 to 36) and meniscal tear (27, 95%CI: 20 to 35). In IPD,
standardised PROMs each revealed similar group mean scores, but scores within
individuals diverged between PROMs (LoA between -7 to -38 and +25 to 52).
Conclusion: Different standardised PROMs give similar PASS thresholds in group
data. PASS thresholds may be affected more by patient and treatment characteristics
than between PROMs. However, different PROMs give divergent scores within
individuals, possibly reflecting different experiences of pain.