Comparison of first and second wave characteristics and treatment data
| First wave | Second wave | Mean difference (95% CI) | X2 (df) | P value | |
| Baseline characteristics | |||||
| Age (years) | 69.0 (52.0–80.0) | 62.0 (52.0–71.0) | −3.4 (−7.8 to +1.1) | – | 0.14 |
Sex
| 49 (69.0%) 22 (31.0%) | 180 (65.0%) 97 (35.0%) | – | 0.4 (1) | 0.52 |
Ethnicity
| 7 (9.9%) 5 (7.0%) 59 (83.1%) 0 (0.0%) | 27 (9.7%) 7 (2.5%) 165 (59.6%) 78 (28.2%) | – | 28.2 (3) | <0.0001 |
| BMI (kg/m2)* | 28.5 (24.9–33.6) | 29.6 (24.8–34.9) | +0.6 (−1.7 to +2.9) | – | 0.63 |
| Comorbidities, frailty and level of care | |||||
| Hypertension | 31 (43.7%) | 125 (45.1%) | – | 0.05 (1) | 0.83 |
| Diabetes mellitus | 21 (29.6%) | 81 (29.2%) | – | 0.003 (1) | 0.96 |
| Cardiovascular disease | 13 (18.3%) | 77 (27.8%) | – | 2.7 (1) | 0.10 |
| Asthma | 8 (11.3%) | 49 (17.7%) | – | 1.7 (1) | 0.19 |
| COPD | 10 (14.1%) | 25 (9.0%) | – | 1.6 (1) | 0.21 |
No of comorbidities:
| 15 (21.1%) 14 (19.7%) 14 (19.7%) 13 (18.3%) 15 (21.1%) | 56 (20.2%) 71 (25.6%) 48 (17.3%) 49 (17.7%) 53 (19.1%) | – | 1.1 (1) | 0.89 |
Clinical Frailty Score:
| 18 (25.4%) 23 (32.4%) 13 (18.3%) 6 (8.5%) 7 (9.9%) 4 (5.6%) | 132 (47.7%) 71 (25.6%) 30 (10.8%) 23 (8.3%) 9 (3.2%) 12 (4.3%) | – | 15.6 (5) | 0.008 |
| Not eligible for intubation | 37 (52.1%) | 67 (24.2%) | – | 21.0 (1) | <0.0001 |
| Symptoms and severity markers | |||||
| Symptom duration | 8 (5–11) | 8 (6–11) | +0.2 (−1.0 to +1.3) | – | 0.76 |
| ≥60% oxygen on HDU admission | 52 (73.2%) | 214 (77.3%) | – | 0.51 (1) | 0.48 |
| CTPA performed | 35 (49.3%) | 251 (90.6%) | – | 65.9 (1) | <0.0001 |
CT severity score
| 0 (0%) 11 (29.7%) 23 (62.2%) 3 (8.1%) | 5 (2.0%) 131 (52.2%) 113 (45.0%) 2 (0.8%) | – | 16.0 (3) | 0.0012 |
| Pulmonary embolism present | 10 (14.1%) | 22 (7.9%) | – | 12.1 (1) | 0.0005 |
| Lymphocytes on rHDU admission (×109/L) | 0.8 (0.5–1.1) | 0.8 (0.5–1.1) | −0.4 (−1.4 to +0.5) | – | 0.35 |
| CRP prior to rHDU admission (mg/L) | 180.6 (118.0–210.0) | 124.1 (78.1–175.6) | −44.1 (−66.9 to −21.3) | – | 0.0002 |
| D-dimer prior to rHDU admission (µg/L) | 1252 (767–2528) | 892 (603–1466) | −644 (−3530 to +2242) | – | 0.66 |
| Nasal pharyngeal PCR swab results | |||||
Result
| 56 (78.9%) 15 (21.1%) | 274 (98.9%) 3 (1.1%) | – | 46.3 (1) | <0.0001 |
Spike gene testing†
|
| 143 (67.1%) 57 (26.8%) 13 (6.1%) | – | – | – |
| Treatments | |||||
| Dexamethasone | 3 (4.2%) | 266 (96.0%) | – | 271.4 (1) | <0.0001 |
| Remdesivir | 4 (5.6%) | 198 (71.5%) | – | 100.6 (1) | <0.0001 |
| Respiratory support duration | 2 (1–4) | 5 (3–8) | 3.0 (1.8 to 4.2) | – | <0.0001 |
| CPAP as primary respiratory support | 32 (45.1%) | 248 (89.5%) | – | 71.1 (1) | <0.0001 |
| Able to adopt semi-prone or full-prone position | 42 (59.2%) | 237 (85.6%) | – | 24.8 (1) | <0.0001 |
Continuous variables are expressed as median (first quartile, third quartile) or mean±SD and categorical variables are expressed as number (percentage). Differences between the first and second waves were compared via t-tests for continuous variables and χ2 tests for categorical variables.
*Missing for 11 (15.5%) patients in the first wave and 58 (20.9%) patients in the second wave.
†From December 2020, routine nasal pharyngeal swabs, tested by PCR, reported the presence or absence of the spike gene (S-gene), following the emergence of the alpha variant in the UK, suggested by absence of the spike gene.
BMI, body mass index; COPD, chronic obstructive pulmonary disease; CPAP, continuous positive airway pressure; CRP, c reactive protein; CT, computed tomography; CTPA, CT pulmonary angiogram; HDU, high-dependency unit; PCR, polymerase chain reaction; rHDU, respiratory high-dependency unit.