Table 1.
Baseline characteristics and clinical course of infants, according to severe bronchiolitis metabotypes
| Characteristics | Metabotype A (n=79, 8.6%) | Metabotype B (n=72, 7.8%) | Metabotype C (n=363, 39.5%) | Metabotype D (n=177, 19.3%) | Metabotype E (n=227, 24.7%) | P-value |
|---|---|---|---|---|---|---|
| Demographics | ||||||
| Age (month), median (IQR) | 2 (1-3) | 3 (2-5) | 3 (2-6) | 3 (2-6) | 4 (2-7) | <0.001 |
| Female sex | 36 (45.6) | 27 (37.5) | 147 (40.5) | 74 (41.8) | 83 (36.6) | 0.63 |
| Race/ethnicity | 0.13 | |||||
| Non-Hispanic white | 28 (35.4) | 35 (48.6) | 167 (46.0) | 68 (38.4) | 101 (44.5) | |
| Non-Hispanic black | 15 (19.0) | 17 (23.6) | 89 (24.5) | 45 (25.4) | 44 (19.4) | |
| Hispanic | 34 (43.0) | 19 (26.4) | 90 (24.8) | 59 (33.3) | 73 (32.2) | |
| Other or unknown | 2 (2.5) | 1 (1.4) | 17 (4.7) | 5 (2.8) | 9 (4.0) | |
| Prematurity (32-37 weeks) | 14 (17.7) | 12 (16.7) | 67 (18.5) | 39 (22.0) | 39 (17.2) | 0.76 |
| Birth weight (kg), median (IQR) | 3.35 (2.95-3.60) | 3.33 (2.90-3.60) | 3.26 (2.90-3.58) | 3.20 (2.86-3.54) | 3.32 (2.98-3.63) | 0.51 |
| Mode of birth (caesarean delivery) | 24 (31.2) | 25 (35.2) | 126 (35.1) | 65 (36.9) | 71 (31.8) | 0.81 |
| Previous breathing problems (count) | 0.001 | |||||
| 0 | 69 (87.3) | 58 (80.6) | 293 (80.7) | 152 (85.9) | 160 (70.5) | |
| 1 | 6 (7.6) | 9 (12.5) | 61 (16.8) | 18 (10.2) | 51 (22.5) | |
| 2 | 4 (5.1) | 5 (6.9) | 9 (2.5) | 7 (4.0) | 16 (7.0) | |
| Previous ICU admission | 1 (1.3) | 2 (2.8) | 4 (1.1) | 2 (1.1) | 6 (2.6) | 0.56 |
| Child history of eczema | 5 (6.3) | 8 (11.1) | 57 (15.7) | 24 (13.6) | 43 (18.9) | 0.07 |
| Lifetime antibiotic use* | 24 (30.4) | 22 (30.6) | 111 (30.6) | 49 (27.7) | 87 (38.3) | 0.19 |
| Lifetime corticosteroid use* | 8 (10.1) | 13 (18.1) | 52 (14.3) | 27 (15.3) | 38 (16.7) | 0.61 |
| Ever attended daycare | 10 (12.7) | 18 (25.0) | 86 (23.7) | 31 (17.5) | 65 (28.6) | 0.02 |
| Cigarette smoke exposure at home | 7 (8.9) | 12 (16.7) | 55 (15.2) | 28 (15.8) | 35 (15.4) | 0.62 |
| Maternal smoking during pregnancy | 10 (13.0) | 11 (15.7) | 50 (13.9) | 26 (14.8) | 29 (12.9) | 0.97 |
| Parental history of asthma | 24 (30.4) | 25 (34.7) | 119 (32.8) | 54 (30.5) | 82 (36.1) | 0.77 |
| Parental history of eczema | 11 (13.9) | 14 (19.4) | 70 (19.3) | 39 (22.0) | 41 (18.1) | 0.64 |
| Clinical presentation | ||||||
| Weight (kg), median (IQR) | 4.99 (4.20-6.17) | 5.80 (4.70-7.15) | 6.10 (4.70-7.60) | 5.90 (4.80-7.60) | 6.90 (5.30-8.32) | <0.001 |
| Respiratory rate (per minute), median (IQR) | 48 (42-60) | 48 (39-60) | 48 (40-60) | 52 (42-62) | 50 (40-60) | 0.26 |
| Oxygen saturation | 0.50 | |||||
| <88% | 6 (7.7) | 7 (10.1) | 19 (5.3) | 10 (5.7) | 10 (4.5) | 0.50 |
| 88%-89.9% | 1 (1.3) | 5 (7.2) | 14 (3.9) | 7 (4.0) | 6 (2.7) | |
| 90%-93.9% | 9 (11.5) | 7 (10.1) | 51 (14.3) | 30 (17.2) | 38 (17.2) | |
| ≥94% | 62 (79.5) | 50 (72.5) | 272 (76.4) | 127 (73.0) | 167 (75.6) | |
| Blood eosinophilia (≥4%) | 9 (12.7) | 10 (17.9) | 38 (12.0) | 10 (6.2) | 15 (7.8) | 0.06 |
| Any IgE sensitization | 16 (20.3) | 15 (20.8) | 64 (17.6) | 47 (26.6) | 39 (17.2) | 0.13 |
| Aeroallergen sensitization | 0 (0.0) | 1 (1.4) | 6 (1.7) | 3 (1.7) | 4 (1.8) | 0.85 |
| Food allergen sensitization | 16 (20.3) | 14 (19.4) | 60 (16.5) | 44 (24.9) | 36 (15.9) | 0.14 |
| Clinical course | ||||||
| Positive pressure ventilation use† | 4 (5.1) | 2 (2.8) | 14 (3.9) | 14 (7.9) | 15 (6.6) | 0.23 |
| Intensive treatment use‡ | 11 (13.9) | 8 (11.1) | 49 (13.5) | 29 (16.4) | 44 (19.4) | 0.28 |
| Length-of-stay (day), median (IQR) | 2 (1-3) | 2 (1-3) | 2 (1-3) | 2 (1-4) | 2 (1-3) | 0.24 |
| Respiratory virus | ||||||
| Any RSV infection | 66 (83.5) | 61 (84.7) | 294 (81.0) | 155 (87.6) | 173 (76.2) | 0.05 |
| Any rhinovirus infection | 13 (16.5) | 9 (12.5) | 79 (21.8) | 27 (15.3) | 57 (25.1) | 0.04 |
| Rhinovirus-A | 6 (7.6) | 5 (6.9) | 31 (8.5) | 15 (8.5) | 31 (13.7) | 0.20 |
| Rhinovirus-B | 3 (3.8) | 0 (0.0) | 5 (1.4) | 2 (1.1) | 5 (2.2) | 0.36 |
| Rhinovirus-C | 6 (7.6) | 3 (4.2) | 41 (11.3) | 8 (4.5) | 23 (10.1) | 0.05 |
Abbreviations: ICU, intensive care unit; IgE, immunoglobulin E; IQR, interquartile range; RSV, respiratory syncytial virus
Data are no. (%) of infants unless otherwise indicated. Percentages may not equal 100, because of rounding and missingness.
*
Any systemic antibiotic or corticosteroid use from birth up to the index hospitalization for bronchiolitis.
†
Infants with severe bronchiolitis who underwent continuous positive airway ventilation and/or mechanical ventilation.
‡
Infants with severe bronchiolitis who were admitted to ICU and/or who underwent positive pressure ventilation.