Functional Status Score for the ICU: An International Clinimetric Analysis of Validity, Responsiveness, and Minimal Important Difference

Abstract

Objective To evaluate the internal consistency, validity, responsiveness, and minimal important difference of the Functional Status Score for the Intensive Care Unit (FSS-ICU), a physical function measure designed for the intensive care unit (ICU). Design Clinimetric analysis. Settings Five international data sets from the United States, Australia, and Brazil. Patients 819 ICU patients. Intervention None. Measurements and Main Results Clinimetric analyses were initially conducted separately for each data source and time point to examine generalizability of findings, with pooled analyses performed thereafter to increase power of analyses. The FSS-ICU demonstrated good to excellent internal consistency. There was good convergent and discriminant validity, with significant and positive correlations (r = 0.30 to 0.95) between FSS-ICU and other physical function measures, and generally weaker correlations with non-physical measures (|r| = 0.01 to 0.70). Known group validity was demonstrated by significantly higher FSS-ICU scores among patients without ICU-acquired weakness (Medical Research Council sumscore ≥48 versus <48) and with hospital discharge to home (versus healthcare facility). FSS-ICU at ICU discharge predicted post-ICU hospital length of stay and discharge location. Responsiveness was supported via increased FSS-ICU scores with improvements in muscle strength. Distribution-based methods indicated a minimal important difference of 2.0 to 5.0. Conclusions The FSS-ICU has good internal consistency and is a valid and responsive measure of physical function for ICU patients. The estimated minimal important difference can be used in sample size calculations and in interpreting studies comparing the physical function of groups of ICU patients.

Relação entre força muscular periférica e funcionalidade em pacientes críticos

“…A inatividade física resulta em perda de massa muscular e força de 1 a 5% por dia de internação na UTI em pacientes críticos, após sete dias de internação diminui cerca de 20% da força muscular e a cada semana subsequente diminui mais 20% 5, [23][24][25] . Em virtude disso é realmente desafiador detectar diferenças estatísticas no início da doença crítica.…”

Construct validity of the Functional Status Score for the Intensive Care Unit: a prospective observational study using actigraphy in mechanically-ventilated patients

“…The FSS-ICU was designed for the ICU setting to quantify the level of physical assistance required by the patient when performing five activities: rolling, transfer from supine to sit, sitting at the edge of the bed, transfer from sitting to stand, and walking. Each activity is scored using an 8-point ordinal scale ranging from 0 (not able to perform) to 7 (complete independence); therefore, the overall score ranges from 0 to 35 points with higher scores indicating greater functional independence [10].…”

“…In the ICU setting, 60 instruments focused on the measurement of physical functioning have been identified, of which 38 measure the mobility domain [3]. Based on their clinimetric properties, four instruments measuring mobility and designed for the ICU setting have been recommended [4,5]: Chelsea Critical Care Physical Assessment Tool (CPAx) [6], Intensive Care Unit Mobility scale (IMS) [7], Physical Function in Intensive Care Unit Test-scored (PFIT-s) [8] and Functional Status Score for the Intensive Care Unit (FSS-ICU) [9,10]. Of these four instruments, FSS-ICU is the only one that assesses the level of physical assistance required by the patient when performing functional activities on the bed, out of bed and walking.…”

“…The FSS-ICU is a widely used instrument because it is available in English [10], Portuguese [11], Turkish [12] and Spanish [13], and its reliability, validity, responsiveness and interpretability have been evaluated in multiple studies [10,14,15], although not specifically for the Chilean-Spanish version.…”

“…The validity of the FSS-ICU has been assessed through correlation analysis against other physical functioning measurement instruments, such as the Medical Research Council Sum Score (MRC-SS) (r 2 = 0.32 to 0.81), the Activities of Daily Living (r 2 = 0.39 to 0.86), the Instrumental Activities of Daily Living (r 2 = 0.48 to 0.57), PFIT-s (rho = 0.85 to 0.87) and the IMS (rho = 0.46 to 0.95) [10,15].…”