TABLE 1.
Associations between Plasma IL-6, Asthma Outcome Measures, and Baseline Markers of Inflammation
| Low IL-6 | Med-Low IL-6 | Med-High IL-6 | High IL-6 | p-value** | |
|---|---|---|---|---|---|
| Cross-sectional* | (n=39 ) | (n= 39) | (n= 39) | (n= 38) | |
| Clinical Outcome Measures | |||||
| BMI Percentile, mean (SD) | 63.2 ± 27.4 | 79.3 ± 20.8a | 84.8 ± 19.3a | 78.1 ± 30.8a | <0.001 |
| Asthma exacerbation in the past yr, mean (SD)*** | 1.1 ± 1.2 | 2.1±2.8 | 2.5±3.3 | 1.8±1.9 | 0.13 |
| Health care utilization for asthma in the past yr, n (%) | 23 (59) | 24 (62) | 23 (59) | 24 (63) | 0.98 |
| ER visit for asthma in the past yr, n (%) | 16 (41) | 22 (56) | 23 (59) | 18 (47) | 0.72 |
| Hospitalization for asthma in the past yr, n (%) | 9 (23) | 12 (31) | 7 (18) | 11 (29) | 0.40 |
| Missed days of school in the past yr, mean (SD) | 3.8 ± 8.6 | 2.8 ± 6.6 | 4.8 ± 14.7 | 2.0 ± 4.1 | 0.64 |
| Severe asthma, n (%)§ | 20 (51) | 25 (64) | 21 (54) | 23 (61) | 0.54 |
| Spirometry Outcome Measures | |||||
| FEV1 (% predicted), mean (SD) | 93.8 ± 11.4 | 89.8 ± 13.6 | 90.2 ± 16.1 | 88.1 ± 15.0 | 0.22 |
| FVC (% predicted), mean (SD) | 105.5 ± 9.9 | 102.3 ± 15.1 | 104.0 ± 10.5 | 102.2 ± 15.9 | 0.21 |
| FEV1/FVC, mean (SD) | 77.8 ± 7.3 | 77.0 ± 9.2 | 75.7 ± 9.5 | 76.1 ± 9.3 | 0.85 |
| FEV1 (% predicted) max. absolute reversibility, mean (SD) | 10.8 ± 11.5 | 11.2 ± 9.5 | 15.6 ± 15.8 | 11.7 ± 12.3 | 0.50 |
| Non-Th2 Biomarkers | |||||
| Plasma CRP log10, mean (SD) | 10.9 ± 1.3 | 11.7 ± 1.3 | 12.4 ± 1.1b | 12.9 ± 1.5b | <0.001 |
| Total white blood cells (K/uL), mean (SD) | 6.3 ± 2.2 | 6.8 ± 2.8 | 7.1 ± 1.9 | 7.5 ± 2.0 | 0.71 |
| Blood neutrophils (cells/uL), mean (SD) | 2933 ± 2068 | 3332 ± 2467 | 3587 ± 1673 | 3945 ± 1713 | 0.71 |
| Sputum neutrophils (%), mean (SD) | 35.4 ± 17.7 | 49.4 ± 25.9 | 42.2 ± 24.2 | 58.6 ± 21.7 | 0.27 |
| Th2 Biomarkers | |||||
| Blood eosinophils (cells/uL), mean (SD) | 472 ± 332 | 362 ± 268 | 362 ± 290 | 383 ± 285 | 0.45 |
| Sputum eosinophils (%), mean (SD) | 17.2 ± 25.4 | 5.2 ± 7.8 | 5.7 ± 15.2 | 3.3 ± 5.0 | 0.54 |
| Serum IgE Measures | |||||
| IgE (kU/L), mean (SD) | 916 ± 1186 | 740 ± 1356 | 867 ± 1614 | 938 ± 1141 | 0.96 |
| ≥ 1 positive specific IgE, n (%) | 36 (92) | 32 (84) | 36 (95) | 34 (92) | 0.43 |
| FENO (ppb), mean (SD) | 40.2 ± 37.8 | 35.5 ± 25.1 | 35.7 ± 41.9 | 31.2 ± 44.5 | 0.84 |
=p<0.01 vs. Low IL-6;
= p<0.001 vs. Low IL-6
There was full data for all outcomes (n=155) with exception of 40 sputum samples, 146 IgE samples, 152 specific IgE, and 152 FENO samples
The p values were generated from linear, logistic, and negative binomial regression models, adjusted for BMI status (healthy weight, overweight, obese) and gender.
Asthma exacerbation was defined as a burst of systemic corticosteroid lasting ≥ 3 days for treatment of worsening asthma control.
The classification of severe asthma was determined using criteria from the American Thoracic Society/European Thoracic Society guidelines.
Abbreviations: BMI = body mass index; FVC = forced vital capacity; FEV1 = forced expiratory volume in 1 second; FEF25-75 = forced expiratory flow between the 25th and 75th percentile of forced vital capacity; SD = standard deviation; CRP = C-reactive protein; IgE = Immunoglobulin E; FENO = fraction of exhaled nitric oxide; ppb = parts per billion