Table 1.
Baseline characteristics and clinical course of infants, according to respiratory syncytial virus bronchiolitis endotypes.
| Characteristics | Overall (n = 221; 100%) |
Endotype A (n = 43; 19.5%) |
Endotype B (n = 63; 28.5%) |
Endotype C (n = 63; 28.5%) |
Endotype D (n = 52; 23.5%) |
P value* |
|---|---|---|---|---|---|---|
| Demographics | ||||||
| Age (month), median (IQR) | 3 (2–6) | 2 (1–4) | 4 (2–6) | 4 (2–8) | 3 (1–4) | 0.002 |
| Female sex | 92 (41.6) | 35 (81.4) | 30 (47.6) | 20 (31.7) | 7 (13.5) | <0.001 |
| Race/ethnicity | 0.40 | |||||
| Non-Hispanic white | 92 (41.6) | 21 (48.8) | 17 (27.0) | 32 (50.8) | 22 (42.3) | |
| Non-Hispanic black | 54 (24.4) | 9 (20.9) | 20 (31.7) | 12 (19.0) | 13 (25.0) | |
| Hispanic | 66 (29.9) | 12 (27.9) | 22 (34.9) | 17 (27.0) | 15 (28.8) | |
| Other or unknown | 9 (4.1) | 1 (2.3) | 4 (6.3) | 2 (3.2) | 2 (3.8) | |
| Prematurity (32–37 weeks) | 46 (20.8) | 7 (16.3) | 14 (22.2) | 10 (15.9) | 15 (28.8) | 0.33 |
| Birth weight (kg), median (IQR) | 3.20 (2.85–3.54) | 3.14 (2.92–3.42) | 3.02 (2.81–3.40) | 3.30 (2.92–3.58) | 3.30 (2.68–3.64) | 0.36 |
| Mode of birth (cesarean delivery) | 75 (34.6) | 13 (30.2) | 19 (30.6) | 23 (36.5) | 20 (40.8) | 0.63 |
| Previous breathing problems (count) | 0.26 | |||||
| 0 | 189 (85.5) | 38 (88.4) | 58 (92.1) | 48 (76.2) | 45 (86.5) | |
| 1 | 24 (10.9) | 3 (7.0) | 4 (6.3) | 11 (17.5) | 6 (11.5) | |
| 2 | 8 (3.6) | 2 (4.7) | 1 (1.6) | 4 (6.3) | 1 (1.9) | |
| Previous ICU admission | 4 (1.8) | 0 (0) | 0 (0) | 3 (4.8) | 1 (1.9) | 0.21 |
| Lifetime antibiotic use† | 67 (30.3) | 2 (4.7) | 12 (19.0) | 48 (76.2) | 5 (9.6) | <0.001 |
| Ever attended daycare | 66 (29.9) | 13 (30.2) | 21 (33.3) | 18 (28.6) | 14 (26.9) | 0.89 |
| Cigarette smoke exposure at home | 32 (14.5) | 11 (25.6) | 11 (17.5) | 6 (9.5) | 4 (7.7) | 0.06 |
| Maternal smoking during pregnancy | 30 (13.8) | 8 (18.6) | 6 (9.7) | 10 (15.9) | 6 (12.2) | 0.56 |
| Parental history of asthma | 68 (30.8) | 6 (14.0) | 50 (79.4) | 10 (15.9) | 2 (3.8) | <0.001 |
| Parental history of eczema | 41 (18.6) | 9 (20.9) | 14 (22.2) | 13 (20.6) | 5 (9.6) | 0.27 |
| Clinical presentation | ||||||
| Weight (kg), median (IQR) | 5.90 (4.60–7.90) | 4.90 (4.14–5.65) | 6.20 (5.18–7.75) | 6.73 (4.90–8.35) | 5.64 (4.40–7.26) | 0.003 |
| Respiratory rate (per minute), median (IQR) | 48 (40–60) | 52 (41–61) | 48 (40–62) | 45 (38–53) | 52 (44–60) | 0.045 |
| Oxygen saturation | 0.28 | |||||
| <90% | 27 (12.6) | 5 (11.9) | 4 (6.3) | 12 (20.3) | 6 (11.8) | |
| 90–93% | 173 (80.5) | 35 (83.3) | 55 (87.3) | 44 (74.6) | 39 (76.5) | |
| ≥94% | 15 (7.0) | 2 (4.8) | 4 (6.3) | 3 (5.1) | 6 (11.8) | |
| Blood eosinophilia (≥4%) | 18 (9.7) | 5 (13.5) | 5 (9.8) | 3 (5.8) | 5 (11.1) | 0.64 |
| IgE sensitization | 46 (20.8) | 7 (16.3) | 15 (23.8) | 16 (25.4) | 8 (15.4) | 0.48 |
| Clinical course | ||||||
| Positive pressure ventilation use‡ | 17 (7.7) | 2 (4.7) | 3 (4.8) | 12 (19.0) | 0 (0) | 0.001 |
| Intensive treatment use§ | 37 (16.7) | 6 (14.0) | 10 (15.9) | 16 (25.4) | 5 (9.6) | 0.15 |
| Length-of-day (day), median (IQR) | 2 (1-3) | 2 (1–3) | 2 (1–4) | 2 (1–4) | 2 (1–3) | 0.17 |
| Antibiotic use during hospitalization | 71 (32.1) | 9 (20.9) | 21 (33.3) | 32 (50.8) | 9 (17.3) | <0.001 |
| Corticosteroid use during hospitalization | 24 (10.9) | 1 (2.3) | 6 (9.5) | 13 (20.6) | 4 (7.7) | 0.02 |
| Respiratory virus | ||||||
| RSV solo infection | 158 (71.5) | 32 (74.4) | 44 (69.8) | 40 (63.5) | 42 (80.8) | 0.22 |
| Rhinovirus coinfection | 29 (13.1) | 5 (11.6) | 13 (20.6) | 5 (7.9) | 6 (11.5) | 0.21 |
| Rhinovirus-A | 14 (6.3) | 1 (2.3) | 7 (11.1) | 5 (7.9) | 1 (1.9) | 0.15 |
| Rhinovirus-B | 4 (1.8) | 2 (4.7) | 1 (1.6) | 0 (0.0) | 1 (1.9) | 0.37 |
| Rhinovirus-C | 11 (5.0) | 2 (4.7) | 5 (7.9) | 0 (0.0) | 4 (7.7) | 0.09 |
| Other coinfection pathogens‖ | 34 (15.4) | 6 (14.0) | 6 (9.5) | 18 (28.6) | 4 (7.7) | 0.006 |
| Chronic comorbidities | ||||||
| Asthma at age 5 years | 51 (23.1) | 4 (9.3) | 24 (38.1) | 12 (19.0) | 11 (21.2) | 0.005 |
| Recurrent wheeze by age 3 years | 69 (31.2) | 10 (23.3) | 22 (34.9) | 19 (30.2) | 18 (34.6) | 0.58 |
IQR interquartile range, ICU intensive care unit, RSV respiratory syncytial virus, IgE immunoglobulin E.
Data are no. (%) of infants unless otherwise indicated. Percentages may not equal 100, because of rounding and missingness.
*Two-sided raw P values.
†Any systemic antibiotic use from birth up to the index hospitalization for bronchiolitis.
‡Infants with bronchiolitis who underwent continuous positive airway ventilation and/or mechanical ventilation.
§Infants with bronchiolitis who were admitted to ICU and/or who underwent positive pressure ventilation.
‖Infants with coinfection by non-rhinovirus include adenovirus infection (n = 7), bocavirus (n = 8), endemic coronavirus (n = 15), enterovirus (n = 1), influenza virus (n = 1), human metapneumovirus (n = 4), Mycoplasma pneumonia (n = 1) and parainfluenza virus (n = 3). Since six infants have coinfection with multiple infecting agents, the total number is not equal to 34.