Cutoff Value for the Patient Acceptable Symptom State of the Thai IKDC Subjective Knee Form in Patients After Primary ACL Reconstruction

Abstract

Background: The Patient Acceptable Symptom State (PASS) cutoff is the value on a patient-reported outcome measure beyond which patients consider themselves to be “feeling well.” There are limited data regarding the PASS threshold for non-English versions of the International Knee Documentation Committee–Subjective Knee Form (IKDC-SKF). Purpose: To establish the PASS cutoff for the Thai version of the IKDC-SKF for patients undergoing primary anterior cruciate ligament reconstruction (ACLR) and to identify factors to achieve PASS after surgery. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: Included in this study were patients aged 18 to 50 years who had undergone primary unilateral ACLR between January 2016 and February 2020. After enrollment, patients completed the Thai IKDC-SKF and answered the anchor question for determining the PASS. Results: Questionnaires were sent to 321 patients, of whom 173 (53.9%) responded. The vast majority (156 patients; 90.2%) considered themselves to have achieved the PASS. This group of patients had significantly higher IKDC scores than did those who did not have an acceptable symptom state (79.6 ± 14.2 vs 60.7 ± 16.5; P < .001). The receiver operating characteristic curve of the IKDC score for predicting the PASS had an area under the curve of 0.82 (95% CI, 0.72-0.91). The optimum PASS cutoff of the Thai IKDC-SKF was a score of 74.2 (sensitivity, 0.72; specificity, 0.82). Factors that provided favorable odds for achieving the PASS were the use of a hamstring tendon autograft (odds ratio, 4.1; 95% CI, 1.5-20.6) and the absence of a patellofemoral chondral lesion (odds ratio, 3.8; 95% CI, 1.03-14.1). Conclusion: For patients undergoing ACLR, the cutoff for the PASS of the Thai version of the IKDC-SKF was a score of 74.2. Two surgery-related factors provided favorable odds for achieving the PASS: the use of a hamstring tendon autograft and the absence of a patellofemoral chondral lesion.