Is the ILOAS a Suitable Assessment Tool for Functional Status Evaluation of Patients with Total Knee Arthroplasty during Inpatient Rehabilitation? Reproducibility, Validity and Responsiveness of the ILOAS

Background: The Iowa Level of Assistance Scale (ILOAS) is an assessment for functional status evaluation after total knee replacement. Since the ILOAS is a multi-activity test it may also be a suitable useful parameter for measuring functional status in rehabilitation after total knee replacement. Objective: This study investigated whether the ILOAS is a suitable assessment tool for functional status evaluation after total knee replacement during inpatient rehabilitation. Method: Using the Western Ontario and McMaster Universities Arthroseindex (WOMAC) as reference tests the ILOAS was measured on different days during inpatient rehabilitation. The ILOAS' reproducibility, concurrent validity and responsiveness were measured. Results: 32 patients participated in this study. The intertester reliability was r(s) = 0.757 (p = 0.01); ICC = 0.789 (95% CI = 0.518 - 0.902), the smallest detectable difference (SDD) was 4.7 points (95% LA = -3.7, 6.1), correlation between WOMAC and ILOAS was r(s) = 0.439 (p = 0.014), effect size (ES) of the ILOAS was 1.51 (95% CI = 0.92 - 2.07) and of the WOMAC 1.27 (95% CI = 0.62 - 1.89). The ILOAS total score varied altered by 5 points on average (7 points for full impact, 2 for partial impact). Conclusion: Intertester reliability as well as intertester correlation were moderate to good. WOMAC and ILOAS correlated moderately. Due to the SDD the change between the 2 test intervals (day 1 and day 14) was clinically significant only in patients with permitted full impact.