Poster 355: A Novel Methodology for Establishing Recommended Threshold Values for MCID, SCB, and PASS for PROMs following ACL Reconstruction

Objectives: An abundance of patient reported outcome measure (PROM) thresholds following ACL reconstruction (ACLR) exist in literature. This frustrates efforts to standardize measures like minimal clinically important difference (MCID), substantial clinical benefit (SCB), and patient acceptable symptom state (PASS). While our earlier study identified the most commonly cited threshold values, this paper examines their underlying methodology. We identify the most robust studies from our systematic review, presenting their International Knee Documentation Committee Subjective Knee Form (IKDC) and Knee injury and Osteoarthritis Outcome Score (KOOS) thresholds and calculation methods. Methods: Our systematic review evaluated 42 studies from PubMed, Embase, Medline, Google Scholar, and Cochrane reporting MCID, SCB, and PASS thresholds after ACLR between January 1st, 2000 – June 30th, 2022. We extracted each publication’s methodology, noting if it calculated new thresholds or cited existing values. For studies deriving new values, we determined if they used anchor or distribution-based methods. For studies citing existing thresholds from publications not present in our systematic review, we identified the source texts, assessed them using the same criteria as the systematic review (but allowed non-ACLR studies), and included them in our evaluation. We then ranked the literature according to a predetermined hierarchy, prioritizing anchored studies, receiver operating characteristic (ROC) analyses, and those with higher levels of evidence. Results: IKDC and KOOS subscales represented 63% of reported MCID, 70% of SCB, and 94% of PASS thresholds (Table 1). Given their overwhelming representation, we only present threshold recommendations for those PROMs. 32 (76%) of studies in our systematic review referenced thresholds in literature and we included 3 frequently cited publications not originally part of the systematic. Our final ranking of thresholds included 14 studies. 9 studies determined thresholds via anchor-based methodologies and 7 used distribution-based techniques. For anchored studies, 7 calculated thresholds using the Youden Index, 1 used Mean Change, and 1 used Predictive Minimal Important Change (MICpred). 4 studies provided sufficient evidence to recommend their threshold: Irrgang 2006 (MCID: IKDC), Muller 2016 (PASS: IKDC and KOOS), Ingelsrud 2018 (MCID: KOOS), and Forlenza 2020 (MCID: KOOS; SCB: IKDC and KOOS). Their thresholds and derivation methods are found in Table 2. Conclusions: This study is the first to present recommended MCID, SCB, and PASS values for commonly reported PROMs following ACLR. We recommend relying on threshold values from studies utilizing anchor-based methodologies and ROC analysis. For studies establishing new thresholds, we recommend this technique along with multiple anchor questions, in order to reduce single-selection bias and better stratify response cohorts.