Assessment of the measurement properties of the Brazilian versions of the Functional Status Score for the ICU and the Functional Independence Measure in critically ill patients in the intensive care unit

OBJECTIVE: To compare the measurement properties (internal consistency, intra and interrater reliability, construct validity, and ceiling and floor effects) of the Functional Status Score for the ICU (FSS-ICU) and the Functional Independence Measure (FIM-motor domain). METHODS: In this study of measurement properties, the FSS-ICU and FIM were applied to 100 patients (72.1 ± 15.9 years; 53% male; Sequential Organ Failure Assessment = 11.0 ± 3.5 points, Simplified Acute Physiology Score 3 = 50.2 ± 16.8 points) in an intensive care unit at baseline and after 2 hours by physiotherapist 1 (test and retest) and 30 minutes after baseline by physiotherapist 2. The measurement properties evaluated were internal consistency (Cronbach's alpha), intra- and interrater reliability (intraclass correlation coefficient), agreement (standard error of measurement) and minimum detectable change at a 90% confidence level, ceiling and floor effects (frequency of maximum and minimum scores) and construct validity (Pearson's correlation). RESULTS: The FSS-ICU and FIM presented adequate internal consistency (Cronbach's alpha, FSS-ICU = 0.95 and FIM = 0.86), intra-and interrater reliability for overall FSS-ICU and FIM score (ICC > 0.75), agreement (minimum detectable change at a 90% confidence level: FSS-ICU and FIM = 1.0 point; standard error of measurement: FSS-ICU = 2% and FIM = 1%) and construct validity (r = 0.94; p < 0.001). However, the FSS-ICU and FIM presented ceiling effects (maximum score for 16% of patients for the FSS-ICU and 18% for the FIM). CONCLUSION: The FSS-ICU and FIM present adequate measurement properties to assess functionality in critically ill patients, although they present ceiling effects.