Abstract
Background:
The patient acceptable symptom state (PASS) is a metric used to aid interpretation of patient-reported outcome measures (PROMs) and determine if an acceptable outcome has been achieved. The purpose of this study was to establish the PASS values for the 12-item Knee Injury and Osteoarthritis Outcome Score (KOOS-12) after total knee arthroplasty (TKA).
Methods:
In this retrospective cohort study 1715 patients undergoing primary TKA for osteoarthritis were recruited to a prospective institutional registry with baseline PROMs including the KOOS-12 between January 2020 and October 2024. At 12 months, 1370 patients (80%) repeated PROMs, including a validated five item satisfaction scale. A receiver operating characteristic (ROC) curve analysis was used to validate the patient reported satisfaction anchor of “satisfied” and “not satisfied” using the area under the curve (AUC) measure. PASS thresholds for the KOOS-12 at 1 year were calculated using three methods, the Youden Index, 80% specificity, and adjusted predictive value methods.
Results:
At 1 year after TKA 1257 patients (92%) were satisfied. The satisfaction anchor of “satisfied” and “not satisfied” ROC AUC was >0.8 for all KOOS-12 subset domains. The PASS threshold based on the Youden Index at 1 year for the KOOS-12 was 75 for pain, 88 for function, 67 for quality of life and 76 for the overall score. The KOOS 12 PASS thresholds were achieved by 1043 (76%) for pain, 883 (65%) for function, 956 (70%) for QoL and 947 (69%) for summary
Conclusions:
This study establishes PASS thresholds for the KOOS-12 and its subscales at 1 year after TKA. These findings will offer a useful benchmark for future outcome studies and for clinicians to determine which patients have achieved success after knee arthroplasty.