Exploring the construct validity of the Barthel index in a sample of Spanish hospitalised patients.

Objective: Examine the construct validity of the Barthel Index in adult inpatient units.

Method: A secondary analysis was performed on a sample of 1342 adult patients admitted to inpatient units. A confirmatory factor analysis of the Barthel Index did not confirm its unidimensional structure (CFA-1). Therefore, two methods were explored to find a solution with a better fit. The sequence of the classical exploratory and confirmatory factor analysis methods was carried out (CFA-2). In contrast, a Gaussian graphical model and confirmatory factor analysis (CFA-3) were performed. Three models were compared on the basis of several goodness-of-fit indicators.

Results: CFA-1 results (χ2 = 161,616; P < .001; RMSEA = .183) indicated a poor fit between the model and the data. Exploratory factor analysis provided a model with two dimensions that explained 86% of the variance and improved the goodness-of-fit in CFA-2 (χ2 = 846; P < .001; RMSEA = .133). The Gaussian graphical model, by removing the item 'Bladder', offered a solution with three dimensions that improved the goodness-of-fit compared to the previous models (χ2 = 492; P < .001; RMSEA = .09).

Conclusion: The Barthel Index is not a unidimensional measure of functional capacity when applied to adult inpatient units. The best-fitting model has a three-dimensional structure (Hygiene; Feeding and disposal; Mobility) that relates to the domains of care needs.