PT  - JOURNAL ARTICLE
AU  - Heleen Demeyer
AU  - Miek Hornikx
AU  - Carlos Augusto Marcal Camillo
AU  - Hans Van Remoortel
AU  - Chris Burtin
AU  - Daniel Langer
AU  - Wim Janssens
AU  - Thierry Troosters
TI  - An estimation of the minimal important difference in physical activity for patients with COPD
DP  - 2014 Sep 01
TA  - European Respiratory Journal
PG  - 1914
VI  - 44
IP  - Suppl 58
4099  - http://erj.ersjournals.com/content/44/Suppl_58/1914.short
4100  - http://erj.ersjournals.com/content/44/Suppl_58/1914.full
SO  - Eur Respir J2014 Sep 01; 44
AB  - RationalePhysical activity (PA) is an important outcome in patients with COPD but the minimal important difference (MID) is lacking. Different distribution based techniques are proposed to identify the MID.MethodsPA was measured for 1 week in 97 patients with COPD before and after 3 months of rehabilitation (rehabilitation sample), by accelerometry. In addition test-retest reliability was measured in 37 patients (test-retest sample), by measuring PA for 2 consecutive weeks. Daily amount of steps was chosen as outcome measurement. Cohen's effect size, empirical rule effect size, standard error of measurement (SEM) and 0.5 times SD of the baseline score (0.5SD) were the used distribution-based approaches.ResultsPatient characteristics of both groups are presented in table 1. The ICC of the daily number of steps between 2 consecutive weeks was 0.94. Calculation of the MID resulted in 1008.48 (Cohen's effect size), 968.14 (empirical rule effect size ), 575.86 (SEM) and 1181.08 (0.5SD) steps per day.View this table:Table1:Patient characteristics of rehabilitation and test-retest sample.ConclusionThe minimal important difference of physical activity, as measured by the daily step count, is estimated between 576 and 1181 steps. Supplemental analyses using anchor based methods are needed to confirm this estimation.