Abstract
Purpose
The patient acceptable symptom state (PASS) is a target value on a patient-reported outcome measures (PROM) scale beyond which patients deem themselves to have attained an acceptable outcome. This study aimed to define the PASS thresholds for generic and knee-specific PROMs at 2 years after unicompartmental knee arthroplasty (UKA).
Methods
Prospectively collected data of 955 patients who underwent UKA for medial osteoarthritis at a single institution was reviewed. Patients were assessed preoperatively and 2 years postoperatively using the Knee Society Knee Score (KSKS), Function Score (KSFS), Oxford Knee Score (OKS), SF-36 Physical Component Score (PCS) and Mental Component Score (MCS). Responses to an anchor question assessing patients’ overall rating of treatment results were dichotomized and used to determine if PASS was achieved. PASS thresholds for each PROM were selected based on the Youden index on a receiver operating characteristics (ROC) curve. Sensitivity analyses were performed for different subgroups (by age, gender, BMI), baseline score tertiles and an alternate definition of PASS.
Results
In total, 92.7% reported their current state as acceptable. The areas under the curve (AUC) for ROCs were 0.72–0.83, except for the SF-36 PCS (AUC 0.64), indicating good discriminative accuracy of the other PROMs. PASS thresholds were 85.5 for KSKS, 77.5 for KSFS, 41.5 for OKS, 49.9 for SF-36 PCS and 54.6 for SF-36 MCS. Sensitivity analyses revealed that the thresholds were robust. Patients who attained a PASS were at least 4–5 times more likely to be satisfied and have expectations fulfilled.
Conclusion
PASS thresholds can be used to define treatment success in future outcome studies. At the individual level, they provide clinically relevant benchmarks for surgeons when assessing postoperative recovery.
Level of evidence
III
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Acknowledgements
We would like to acknowledge our physiotherapist colleagues for assisting us with the preoperative and postoperative assessments of the patients.
Funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. IRB: Centralised institutional review board (IRB) approval (CIRB 2020/2157) was obtained for this study.
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Goh, G.S., Liow, M.H.L., Chen, J.Y. et al. The patient acceptable symptom state for the knee society score, oxford knee score and short form-36 following unicompartmental knee arthroplasty. Knee Surg Sports Traumatol Arthrosc 31, 1113–1122 (2023). https://doi.org/10.1007/s00167-021-06592-x
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DOI: https://doi.org/10.1007/s00167-021-06592-x