BACKGROUND
The Early Rehabilitation Barthel Index (ERBI) comprises seven items of the
Early Rehabilitation Index and ten items of the Barthel Index. The ERBI is
usually used to measure functional changes in patients with severe acquired
brain injury (sABI), but its measurement properties have yet to be
extensively assessed.
AIM
To study the unidimensionality and internal construct validity (ICV) of the
ERBI through Confirmatory Factor Analysis (CFA), Mokken Analysis (MA), and
Rasch Analysis (RA).
DESIGN
Multicenter prospective study.
SETTING
Inpatients from five intensive rehabilitation centers.
POPULATION
Two hundred and forty-seven subjects with sABI.
METHODS
ERBI was administered on admission and discharge to study its
unidimensionality through CFA and MA and its ICV, reliability, and targeting
through RA.
RESULTS
The preliminary analyses showed a lack of unidimensionality (RMSEA=0.460
>0.06; SRMR=0.176 >0.06; CFI=1.000 >0.950; TLI=1.000 >0.950).
According to CFA, “Confusional state” and “Behavioral
disturbance” items showed low factor loadings (<0.40), whereas
these two items composed a separate scale within the MA. Furthermore, the
baseline RA showed that three items misfitted (“Mechanical
ventilation,” “Confusional state,” “Behavioral
disturbances”) and a lack of conformity of several ICV requirements.
After deletion of three misfitting items and further non-structural
modifications (
i.e.
, testlets creation to absorb local
dependence between items and item misfit), the solution obtained showed
adequate ICV, adequate reliability for measurements at the individual level
(PSI>0.85), although with a frank floor effect. This final solution was
successfully replicated in a total sample of the subjects. After
post-hoc
modifications of the score structure of two
out of three misfitting items, the subsequent CFA (RMSEA=0.044 <0.06;
SRMR=0.056 <0.06; CFI=1.000 >0.950 TLI=1.000 >0.950) and MA showed
the resolution of the unidimensional issues.
CONCLUSIONS
Although the ERBI is a potentially valuable tool for measuring functioning in
the coma-to-community continuum, our analyses suggested its lack of ICV,
partly due to an incorrect scoring design of some items. A new perspective
multicenter study is proposed to validate a modified version of the ERBI
that overcomes the problems highlighted in this analysis.
CLINICAL REHABILITATION IMPACT
Our results do not support the use of the original structure of the ERBI in
clinical practice and research, as a lack of ICV was highlighted.