Table 2.
Univariate associations between seasonal use of prednisone during the double blind phase and explanatory variables*
| Overall | Fall | Winter | Spring | Summer | Interaction ‡ | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Number (%) of patients with an exacerbation | 151/400 (37.8%) | 65/226 (28.8%) | 34/214 (15.9%) | 56/281 (19.9%) | 27/188 (14.5%) | ||||||
| Baseline Predictors † | OR (95% CI) | P | OR (95% CI) | P | OR (95% CI) | P | OR (95% CI) | P | OR (95% CI) | P | |
| Age (yrs.) | 0.96 (0.89,1.02) | 0.17 | 1.02 (0.91,1.15) | 0.73 | 0.91 (0.78,1.06) | 0.22 | 0.90 (0.82,0.98) | 0.02 | 1.10 (0.94,1.29) | 0.22 | |
| Gender (Male vs. Female) | 0.80 (0.54,1.17) | 0.25 | 0.77 (0.43,1.38) | 0.38 | 0.90 (0.43,1.89) | 0.79 | 0.97 (0.54,1.75) | 0.93 | 0.44 (0.18,1.03) | 0.06 | |
| Race (Black vs. Other) | 0.85 (0.57,1.25) | 0.41 | 0.81 (0.45,1.46) | 0.49 | 1.04 (0.49,2.22) | 0.911 | 0.99 (0.55,1.78) | 0.97 | 0.47 (0.19,1.17) | 0.105 | |
| BMI Percentile (85% or higher vs. not) | 1.16 (0.79,1.73) | 0.44 | 1.18 (0.66,2.13) | 0.57 | 1.28 (0.61,2.69) | 0.52 | 1.10 (0.61,1.98 | 0.74 | 0.98 (0.43,2.23) | 0.97 | |
| Allergen skin tests (no of positive tests of 14) | 1.02 (0.96,1.08) | 0.51 | 1.10 (1.01,1.19) | 0.03 | 0.95 (0.84,1.07) | 0.42 | 1.00 (0.90,1.10) | 0.93 | 0.97 (0.85,1.09) | 0.58 | *** |
| Mite skin tests (Yes vs. No) | 0.75 (0.50,1.10) | 0.14 | 1.37 (0.77,2.45) | 0.28 | 0.56 (0.26,1.19) | 0.13 | 0.59 (0.32,1.07) | 0.09 | 0.67 (0.29,1.56) | 0.35 | |
| Rodent skin tests (Yes vs. No) | 1.34 (0.90,2.01) | 0.14 | 2.05 (1.14,3.68) | 0.02 | 1.11 (0.52,2.37) | 0.78 | 1.03 (0.56,1.87) | 0.93 | 0.85 (0.36,2.01) | 0.71 | |
| Cockroach skin tests (Yes vs. No) | 1.15 (0.77,1.75) | 0.50 | 1.93 (1.03,3.61) | 0.04 | 0.99 (0.47,2.10) | 0.98 | 0.95 (0.51,1.75) | 0.87 | 0.74 (0.31,1.77) | 0.50 | *** |
| Mold skin tests (Yes vs. No) | 1.05 (0.71,1.55) | 0.82 | 1.50 (0.84,2.68) | 0.17 | 0.65 (0.30,1.41) | 0.27 | 0.95 (0.53,1.71) | 0.86 | 1.07 (0.46,2.49) | 0.88 | |
| Total IgE (Log-transformed kU/l) | 1.66 (1.14,2.48) | 0.01 | 1.90 (1.08,3.36) | 0.03 | 1.91 (0.94,3.86) | 0.07 | 1.19 (0.66,2.16) | 0.56 | 1.32 (0.58,2.99) | 0.51 | |
| SIgE Der f (Log-transformed kU/l) | 1.22 (0.98,1.54) | 0.08 | 1.46 (1.02,2.09) | 0.04 | 1.28 (0.83,1.96) | 0.26 | 0.99 (0.71,1.39) | 0.97 | 1.29 (0.83,2.02) | 0.26 | |
| SIgE Der p (Log-transformed kU/l) | 1.21 (0.96,1.52) | 0.10 | 1.43 (0.99,2.05) | 0.05 | 1.29 (0.84,2.00) | 0.25 | 0.98 (0.69,1.39) | 0.92 | 1.27 (0.80,1.99) | 0.31 | |
| SIgE cockroach (Log-transformed kU/l) | 1.17 (0.94,1.47) | 0.15 | 1.48 (1.06,2.06) | 0.02 | 1.08 (0.71,1.63) | 0.72 | 1.03 (0.74,1.44) | 0.85 | 0.98 (0.62,1.55) | 0.92 | |
| SIgE Alternaria (Log-transformed kU/l) | 1.13 (0.90,1.41) | 0.30 | 1.09 (0.77,1.53) | 0.63 | 0.89 (0.57,1.40) | 0.62 | 1.06 (0.76,1.48) | 0.74 | 1.64 (1.02,2.63) | 0.04 | |
| Blood Eosinophils (% of white blood cells) | 1.07 (1.00,1.13) | 0.03 | 1.08 (0.99,1.17) | 0.09 | 1.01 (0.91,1.13) | 0.80 | 1.04 (0.95,1.14) | 0.4 | 1.13 (1.01,1.27) | 0.04 | |
| Previous Season Predictors † | |||||||||||
| Asthma-related symptoms (days in preceding 2 wks.) | 0.98 (0.92,1.04) | 0.51 | 1.00 (0.89,1.12) | 0.95 | 1.03 (0.93,1.15) | 0.59 | 0.99 (0.90,1.09) | 0.84 | 1.00 (0.87,1.14) | 0.98 | |
| ACT® in preceding month (uncontrolled vs. controlled) | 0.85 (0.53, 1.33) | 0.48 | 0.84 (0.36, 1.99) | 0.70 | 1.33 (0.60, 2.94) | 0.48 | 0.80 (0.36,1.76) | 0.58 | 1.03 (0.41,2.62) | 0.95 | |
| FEV1 (% predicted value) | 0.98 (0.97,0.99) | <0.001 | 0.98 (0.96,1.00) | 0.01 | 0.97 (0.95,0.99) | 0.01 | 0.99 (0.97,1.00) | 0.11 | 0.98 (0.96,1.01) | 0.15 | |
| FEV1/FVC (×100) | 0.96 (0.93,0.97) | <0.001 | 0.97 (0.94,1.00) | 0.03 | 0.94 (0.91,0.99) | 0.01 | 0.96 (0.93,0.99) | 0.02 | 0.94 (0.89,0.99) | 0.02 | |
| FeNO (Log-transformed ppb) | 1.61 (0.98,2.68) | 0.06 | 3.63 (1.64,8.04) | 0.001 | 0.56 (0.21,1.49) | 0.25 | 1.06 (0.49,2.31) | 0.89 | 2.54 (0.86,7.53) | 0.09 | *** |
| Exacerbations previous year (Yes vs. No) | 2.61 (1.85,3.68) | <0.001 | 2.89 (1.60,5.23) | < 0.001 | 1.85 (0.89,3.87) | 0.10 | 4.34 (2.26,8.30) | < 0.001 | 1.71 (0.75,3.92) | 0.20 | *** |
| Exacerbations in previous season(Yes vs. No) | 2.50 (1.65,3.61) | <0.001 | 5.37 (2.53,11.39) | < 0.001 | 2.66 (1.21,5.83) | 0.02 | 1.53 (0.73,3.20) | 0.26 | 2.53 (1.05,6.08) | 0.04 | *** |
| Inhaled Corticosteroid Treatment (treatment steps) § | 1.15 (1.04,1.27) | 0.004 | 1.06 (0.90,1.23) | 0.49 | 1.10 (0.91,1.34) | 0.33 | 1.18 (1.01,1.38) | 0.03 | 1.34 (1.06,1.70) | 0.01 | |
| Composite Asthma Severity Index in preceding 2 months | 1.08 (1.00,1.16) | 0.05 | 1.08 (0.94,1.25) | 0.27 | 1.07 (0.93,1.23) | 0.37 | 1.11 (1.00,1.24) | 0.05 | 1.16 (0.99,1.36) | 0.07 | |
Values are odds ratios for exacerbations during each overall/season (columns) for the listed predictors (rows). Predictors are continuous variables unless noted.
For the overall column, all predictors are measured at either study enrollment or randomization. For the seasonal columns (Fall, Winter, Spring and Summer) baseline predictors are measured at study enrollment; the baseline measure is used regardless of the seasonal. Previous season predictors are measured during the season before the exacerbation outcome season; for example, maximum symptom days from the summer are used to predict fall exacerbations and so on.
Test of interaction among the seasonal predictors of exacerbations.
Significant interactions (p<0.10) are noted with the interpretation being that the effect of the predictor is different by season.
Six treatment steps were established, consistent with the guidelines of the National Asthma Education and Prevention Program.13