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

Abstract Objective To evaluate the construct validity (hypotheses testing) of the Chilean-Spanish version of the Functional Status Score for the Intensive Care Unit (FSS-ICU) using continuous actigraphy from intensive care unit (ICU) admission to ICU discharge. Design The Chilean-Spanish version of the FSS-ICU was used in a prospective observational study to mainly evaluate its correlation with actigraphy variables (GT9X Link-ActiGraph). The FSS-ICU was assessed on awakening and at ICU discharge, while actigraphy variables were recorded from ICU admission to ICU discharge. Setting A 12-bed academic medical-surgical ICU. Participants Thirty mechanically-ventilated patients of 92 patients screened. Interventions Not applicable. Main Outcome Measure Construct validity of the FSS-ICU Chilean-Spanish version was assessed by testing 12 hypotheses, including the correlation with activity counts, activity time (>99 counts per minute), inactivity time (0-99 counts per minute), muscle strength, ICU length of stay, and duration of mechanical ventilation. Results The median FSS-ICU was 19 (IQR 10–26) points on awakening and 28.5 (IQR 22–32) at ICU discharge. There was no floor/ceiling effect of the FSS-ICU at awakening (0%/0%) and only a ceiling effect at ICU discharge that was acceptable (0%/10%). Less activity time was associated with better mobility on the FSS-ICU at both awakening (rho = -0.62, P Conclusions The Chilean-Spanish FSS-ICU had a strong correlation with inactivity time during the ICU stay. These findings enhance the available clinimetric properties of the FSS-ICU.