Preoperative Evaluation of the Lower Extremity-Specific PROMIS Mobility Bank in Patients with ACL Tears

PURPOSE: The purpose of this study was to preoperatively assess the Patient-Reported Outcomes Measurement Information System (PROMIS) Item Bank v2.0–Mobility in patients with anterior cruciate ligament (ACL) tears to (1) determine construct validity by correlating with legacy patient-reported outcomes (PROs), (2) evaluate test burden, (3) determine the presence of floor or ceiling effects, and (4) revisit the conventional threshold for inclusiveness (floor/ceiling effects) in the modern era of computer adaptive testing (CAT)–based PROs. METHODS: Patients at a large academic musculoskeletal specialty center diagnosed with ACL tears indicated for surgery were administered the following outcomes measures before surgery: PROMIS Mobility CAT, PROMIS Pain Interference CAT (PROMIS PI), International Knee Documentation Committee (IKDC), the Marx Knee Activity Rating Scale (Marx), and Single Assessment Numeric Evaluation (SANE). Construct validity was evaluated using Spearman correlation coefficients. Correlation strengths were defined as high (≥0.7), high-moderate (0.61-0.69), moderate (0.4-0.6), moderate-weak (0.31-0.39) and weak (≤0.3). Number of questions to completion were recorded as a marker of test burden. The percentage of patients scoring at the extreme high (ceiling) or low (floor) of each measure was recorded to measure inclusivity. RESULTS: A total of 1126 patients were evaluated. The mean number of questions answered (± standard deviation) was 4.7 ± 2.1 for PROMIS Mobility and 4.5 ± 1.9 for PROMIS PI. PROMIS Mobility demonstrated a high correlation with IKDC, (r = 0.81, P < .001), a high-moderate correlation with PROMIS PI (r = −0.63), and a moderate correlation with SANE (r = 0.46, P < .01). Neither PROMIS Mobility nor PROMIS PI met conventional criteria for floor or ceiling effects (>15%). CONCLUSIONS: The PROMIS Mobility measure maintains construct validity, because its scores correlate strongly with other PROs measuring physical function with high efficiency among preoperative patients with ACL injuries. Although ceiling effects of PROMIS Mobility CAT were below the conventional significance threshold of 15% at the preoperative timepoint in this population, this study provides critical feedback for redesigning the Mobility bank. LEVEL OF EVIDENCE: Level III (Diagnostic study).