Journal of Rehabilitation Medicine 51-8 | Page 30

J Rehabil Med 2019; 51: 566–574
ORIGINAL REPORT
RASCH ANALYSIS OF THE UK FUNCTIONAL ASSESSMENT MEASURE IN
A SAMPLE OF PATIENTS WITH TRAUMATIC BRAIN INJURY FROM THE UK
NATIONAL CLINICAL DATABASE
Lynne TURNER-STOKES, DM, FRCP 1,2 , Oleg N. MEDVEDEV, PhD 3,4 and Richard J. SIEGERT, PhD 4
From the 1 King’s College London, Department of Palliative Care, Policy and Rehabilitation, Faculty of Life Sciences and Medicine,
2
Regional Hyper-acute Rehabilitation Unit, Northwick Park Hospital, London North West Healthcare NHS Trust, London, UK, 3 University
of Waikato, School of Psychology, and 4 Auckland University of Technology, School of Public Health & Psychosocial Studies and School
of Clinical Sciences, Auckland, New Zealand
Objective: To determine whether the UK Functional
Assessment Measure (UK FIM+FAM) fits the Rasch
model in patients with complex disability following
traumatic brain injury.
Design: Psychometric evaluation including prelimi-
nary exploratory and confirmatory factor analyses
followed by Rasch analysis.
Participants: A multicentre UK national cohort of
1,956 patients admitted for specialist rehabilitation
following traumatic brain injury.
Results: The suitability of the Partial Credit Mo-
del was confirmed by the likelihood-ratio test (χ 2
(df86) =7,325.0, p  < 0.001). Exploratory and confir-
matory factor analyses supported 3 factors (Motor,
Communication, Psychosocial). Rasch analysis of
the full scale incorporating the 3 factors as super-
items resulted in an acceptable overall model fit (χ 2
(df24)=36.72, p  = 0.05) and strict uni-dimensiona-
lity when tested on a sub-sample of n  = 320. These
results were replicated in a full sample (n  = 1,956)
showing uni-dimensionality and good reliability with
Person Separation Index = 0.81, but item trait inte-
raction was significant due to the large sample size.
No significant differential item functioning was ob-
served for any personal factors. Neither uniform re-
scoring of items nor exclusion of participants with
extreme scores improved the model fit.
Conclusion: The UK FIM+FAM scale satisfies the
Rasch model reasonably in traumatic brain injury.
A conversion table was produced, but its usefulness
in clinical practice requires further exploration and
clinical translation.
Key words: Rasch analysis; functional assessment measure;
rehabilitation; outcome; traumatic brain injury.
Accepted Jun 14, 2019; Epub ahead of print Jun 27, 2019
J Rehabil Med 2019; 51: 566–574
Correspondence address: Lynne Turner-Stokes, King’s College London,
Department of Palliative Care, Policy and Rehabilitation, Faculty of Life
Sciences and Medicine, London, UK. E-mail: lynne.turner-stokes@doc-
tors.org.uk
O
utcome measurement is a key requirement for
rehabilitation services to support comparison
of programmes, practices and populations. Trauma-
tic brain injury (TBI) poses particular challenges
LAY ABSTRACT
The UK Functional Assessment Measure (UK FIM+FAM)
is a scale used to evaluate the outcome of rehabilitation
after acquired brain injury as part of the UK Rehabili-
tation Outcomes Collaborative (UKROC). The FIM+FAM
is administered by clinicians and measures how well
people are recovering their independence. It has 30 se-
parate questions concerning a person’s physical (e.g.
eating, toileting, bathing) and cognitive (e.g. expres-
sion, memory, safety awareness) independence. Data
from 1,956 UK patients who had survived a traumatic
brain injury were analysed. The main purpose of this
study was to establish that the FIM+FAM meets some of
the stringent technical standards for clinical and scien-
tific measurement. A statistical method known as Rasch
analysis was used to demonstrate that the FIM+FAM
produces accurate and reliable scores. The results sho-
wed that the FIM+FAM is a practical and useful scale
for measuring change in people in rehabilitation after a
traumatic brain injury.
for outcome evaluation in rehabilitation. As well as
improvement in independence for activities of daily
living, measurement tools need to encompass chan-
ges in cognitive, communicative and psychosocial
function, which are often the main factors that limit
independence following TBI.
The Functional Independence Measure (FIM™)
(1, 2) is an 18-item measure of functional indepen-
dence, which is widely used as a measure of outcome
from rehabilitation. Although 5 of the items address
elements of communication and cognitive function,
its predominant focus is on physical function and it
has well recognized ”ceiling” effects (3). The Fun-
ctional Assessment Measure (FAM) was developed
in the 1990s specifically for more ambulant patients
with TBI. It adds 12 items to the FIM scale, mainly
addressing cognitive and psychosocial function, with
the intent of extending the range of difficulty in this
group (3, 4). From a scaling perspective, the FAM
items as a whole may have little impact on the ceiling
effects of the FIM™ in higher functioning patients (5),
but from a clinical perspective they may still provide
useful information about the less visible aspects of
neurological disability for patients at all levels (6).
This is an open access article under the CC BY-NC license. www.medicaljournals.se/jrm
doi: 10.2340/16501977-2580
Journal Compilation © 2019 Foundation of Rehabilitation Information. ISSN 1650-1977