Feasibility, Reliability, Responsiveness, and Validity of the Patient-Reported Functional Scale for the Intensive Care Unit: A Pilot Study

BACKGROUND: Although many performance-based measures assess patients' physical function in intensive care unit (ICU) survivors, to our knowledge, there are no patient-reported ICU rehabilitation-specific measures assessing function. We developed the Patient-Reported Functional Scale-ICU (PRFS-ICU), which measures patients' perceptions of their ability to perform 6 activities (rolling, sitting edge of bed, sit-to-stand and bed-to-chair transfers, ambulation, and stair climbing). Each item is scored from 0 (unable) to 10 (able to perform at pre-ICU level) to a maximum of 60. OBJECTIVES: Estimate the feasibility, reliability, responsiveness, and validity of the PRFS-ICU. METHODS: This was a substudy of TryCYCLE, a single-center, prospective cohort examining the safety and feasibility of early in-bed cycling with mechanically ventilated patients (NCT01885442). To determine feasibility, we calculated the number of patients with at least 1 PRFS-ICU assessment during their hospital stay. To assess reliability, 2 raters blinded to each other's assessments administered the PRFS-ICU within 24-hours of each other. We calculated the intraclass correlation coefficient (ICC; 95% confidence interval [CI]), standard error of measurement (SEM, 95% CI), and minimal detectable change (MDC₉₀). To assess validity, we estimated convergent validity of the PRFS-ICU with the Functional Status Score for ICU (FSS-ICU), Medical Research Council Sum Score (MRC-SS), Physical Function Test for ICU (PFIT-s), Katz Index of Independence in Activities of Daily Living (Katz ADLs), and a pooled index using Pearson's correlation coefficient (r, 95% CI). RESULTS: Feasibility: 20 patients completed a PRFS-ICU assessment. Reliability and responsiveness: 16 patients contributed data. The ICC, SEM, and MDC₉₀ were 0.91 (0.76, 0.97), 4.75 (3.51, 7.35), and 11.04 points, respectively. Validity: 19 patients contributed data and correlations were (r [95% CI]): FSS-ICU (0.40 [-0.14, 0.76]), MRC-SS (0.51 [0.02, 0.80]), PFIT-s (0.43 [-0.13, 0.78]), Katz ADLs (0.53 [0.10, 0.79]), and pooled index (0.48 [-0.14, 0.82]). CONCLUSIONS: Our pilot work suggests the PRFS-ICU may be a useful tool to assess and monitor patients' perceptions of function over time.