Page 62 - Comprehensive treatment of patients with glucocorticoid-dependent severe asthma

Chapter 3
Power
As a clinical meaningful difference on the HADS scale we defined a 2-unit difference. Because the HADS has a standard deviation of 4 [25], we needed to include 128 patients in total to achieve 80% power for this medium effect size (significance level 0.05). As a clinical meaningful difference on the NEO- FFI scale we defined a 3-unit difference. Because the NEO-FFI has a standard deviation of 6 [27], we needed to include 128 patients in total to achieve 80% power for this medium effect size (significance level 0.05).
Results
Patient characteristics
One-hundred-eighty-seven patients, 67 patients with severe, prednisone- dependent asthma (20-77 yr), 47 with severe non-prednisone dependent asthma (19-70 yr) and 73 patients with mild-moderate asthma (18-75 yr) participated in the study.
There was no significant difference between the prednisone-dependent patients and the group of severe, non prednisone-dependent patients and mild-moderate asthma patients with respect to gender, BMI and atopy (Table 1). However, prednisone-dependent asthma patients were older, had longer asthma duration and showed more severe airflow limitation as compared to the other patients.
Psychological characteristics in prednisone-dependent vs severe non- prednisone dependent and mild-moderate asthma
Patients with severe prednisone-dependent asthma had significant higher scores on depression symptoms (HADS-D mean (SD) 4.5 (3.6) vs. 2.4 (2.4) and 3.4 (2.5), p = 0.002) and showed a trend towards higher anxiety symptoms (HADS-A 6.2 (4.4) vs. 4.8 (3.6) and 5.0 (2.9), p = 0.06) as compared to patients with severe or milder disease resp. (table 2).
The prevalence of clinically significant depressive symptoms (HADS-D score ≥11) and anxiety symptoms (HADS-A score ≥11) was higher in patients with severe, prednisone dependent asthma than in patients with severe
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