The BASFI
is a set of 10 questions designed to determine the degree of functional
limitation in those with AS. The research team recognised that although
treatment is focused on pain control and the improvement of function,
the available methods of assessing function were not specific to AS
and were inadequately validated. The team also state that:
“after
pain and stiffness, one of the most important complaints of patients
with AS is disability.” (Calin et al,
1994, p2281).
The ten questions were chosen with a major input from
patients with AS. The first 8 questions consider activities related
to functional anatomy. The final 2 questions assess the patients’
ability to cope with everyday life.
A 10cm visual analog scale is used to answer the questions
(refer to page 11). The authors believe that this improves both the
sensitivity of the index to change and its capacity to elicit a range
of responses across the entire scale (Calin et al, 1994). The mean
of the ten scales gives the BASFI score – a value between 0
and 10.
Using a sample of 47 inpatients and 116 outpatients,
the authors compared the BASFI with the Dougados functional index.
Results showed:
BASFI and Dougados took an equivalent amount of time
to complete (100 secs max.).
Subjects expressed no preference for either instrument.
The BASFI scores illustrated a better distribution
– 0 to 9.5 compared with 0 to 6.5 for Dougados.
The reproducibility of both scores was statistically
significant (p<0.001).
Inter-observer reliability was statistically significant
(p<0.001) for both scores.
Over a 3 week treatment period:
........- the BASFI scores demonstrated
a significant (p=0.004) 19.6%
...........improvement
........- however the 5.9% improvement
in the Dougados scores was
...........insignificant.
(Calin et al, 1994).
Results
3 and 6 demonstrate the benefits of the BASFI over the Dougados index.
“The BASFI scores produced a normal distribution which covered
95% of the total scale whereas the Dougados functional index used
only 65% of the total range” (Calin et al, 1994, 2285). Perhaps
this can be explained through the use of the visual analog scale.
The Dougados index only gives patients three choices of answer to
the question “can you?” of the 20 activities listed. The
choices being:
- “Yes, with no difficulty”
- “Yes, but with difficulty”
- “No”
The middle
option (yes, but with difficulty) is very vague and does not distinguish
between minor and major degrees of difficulty. A visual analog scale
accommodates a broader range of possible answers with greater ease,
and therefore gives a better representation of the assessed population.
The use of the visual analog scale can also explain the greater degree
of sensitivity to change shown by the BASFI. A scale allows for smaller
changes to be identified than the 3 choice answer system.
Ruof et al (1999) have compared the responsiveness
of BASFI, the Dougados Functional Index and the AS specific version
of the Health Assessment Questionnaire. They conducted a double-blind,
placebo-controlled study. 174 patients were included and received
either a placebo, vitamin E or diclofenac. The authors found BASFI
to be more responsive than either of the other two indices for both
improvements and deterioration. The authors suggested that this is
because the BASFI demonstrates a better baseline distribution pattern
and the visual analog scale allows for greater sensitivity. This supports
the findings of Calin et al (1994).
To conclude, the BASFI is quick, easy, reliable and
sensitive to change across the whole disease spectrum (Calin et al,
1994).
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