Ulla Werlauff Methods to assess physical functioning - Danske ...

Visual Analog Scale (study IV)
The Visual Analog Scale (VAS) is used to measure a variety of subjective phenomena, among them
fatigue. The score is rated on a 100 mm horizontal line with descriptions at each end, and represents
the patient’s perception on the phenomenon. The reliability of a VAS scale to measure fatigue
severity has been presented in healthy individuals and patients with sleep-disorder [Lee 1991] and
in patients with stroke [Tseng 2010].
Focus-groups (study IV)
Focus-groups were used to assess the content validity of the FSS and its relevance to measure
impact of fatigue in patients with CM. A purposive sampling was performed to identify patients
with FSS score ≥ 4; among these patients, 16 were randomly selected and invited to participate in
one of two focus-group interviews. Interviews were based on an interview-guide with six main
themes. For each theme, a set of 2-6 sub-questions were constructed, in case the group needed
inspiration for the discussions. At the end of the discussion, the participants could add further
comments on a piece of paper or write information they wouldn’t bring up in the group. After a
short break, the FSS was handed to each of the participants, who were then asked to comment on
whether fatigue according to their perception was contained in the FSS , and if not – which
dimensions of fatigue was not captured in the scale. The focus-group interviews were recorded on
tape.
Data analyses / Statistics
Statistical analyses was conducted by means of Statistical Package for the Social Sciences (SPSS
16.0) in study I, SAS 9.2 software package (SAS Institute Inc) in studies II and III, and Stata
version 11.2 in study IV. Significance levels were set at p < 0.05, using two-tailed testing. Nonparametric
statistics were used when criteria for normal distribution were not met, and when the
sample size was small. For calculation of unpaired differences between groups, Mann-Whitney U
test was used in studies I and II and the parametric analogue, student t-test, in study IV. To calculate
paired differences within groups, Wilcoxon signed rank test was used in studies I and III. Kruskal
Wallis’ test was used to calculate differences among groups in study II. Linear regression analyses
were used to test longitudinal data in study III. Spearman’s rank order correlation coefficient (r s )
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