Article

Clinician-reported outcome instruments such as the North Star Ambulatory
Assessment (NSAA) need to be able to detect clinically important change to be
suitable for clinical trials. However, in Duchenne muscular dystrophy (DMD),
identifying changes in function is not straightforward. In this study, we use
Rasch-transformed data to examine the responsiveness and minimal important
difference (MID) of the NSAA in males with DMD receiving different corticosteroid
regimes. METHOD: NSAA data were examined from 198 males (mean age at assessment
was 8y 6mo [SD 2y 6mo] range 4y-18y; 805 assessments). Responsiveness was
assessed using mean score changes (using Rasch-transformed data) between adjacent
pairs of age groups, pairwise squared t-values from paired samples t-tests, and
an effect size calculation. The MID was assessed using the effect size
calculation and 0.5 standard deviation (SD) of mean score differences. RESULTS:
Our findings revealed a difference in change scores over time between the two
corticosteroid regimes. Mean NSAA person estimates were higher in the daily
prednisolone group. The mean MID (0.5 SD) was 8.8 and 6.9 for the daily group and
intermittent group respectively. INTERPRETATION:
This study, based on
Rasch-transformed NSAA data, provides an initial basis for the interpretation of
clinical change in DMD over time and between corticosteroid regimes. Our proposed
MIDs can be mapped back to differences in specific item content across the range
of the NSAA.
CI - (c) 2013 Mac Keith Press.

Langue : ANGLAIS