Sensitivity analysis—overall and subpopulation estimates of AFARDS, AFAHRF and AFAHRF-UL
| Sensitivity analysis | Model 1: AFARDS
(non-AHRF controls) | Model 2: AFARDS (AHRF-UL controls) | Model 3: AFAHRF
(non-AHRF controls) | Model 4: AFAHRF-UL
(non-AHRF controls) | |
| Unmatched analysis | Unmatched analysis | Matched analysis—hospital mortality as outcome | Unmatched analysis | Unmatched analysis | |
| Patients with ARDS/AHRF | 2653 | 2653 | 851 | 3504 | 851 |
| Controls | 8407 | 851 | 851 | 8407 | 8407 |
| Overall AF | 25.2% (22.7%–27.6%) | 22.3% (14.4%–30.1%) | 17.7% (7.7%–27.6%) | 26.5% (23.9%–29.1%) | 5.9% (4.1%–7.7%) |
| PaO2/FiO2 ratio (mm Hg) | |||||
| >200 | 8.9% (4.5%–13.4%) | 10.7% (−1.6%–23.0%) | 25.8% (7.6%–43.9%) | 10.6% (6.3%–15.0%) | 2.5% (=2.5%–7.5%) |
| 100–200 | 17.2% (13.4%–21.1%) | 23.6% (13.2%–34.0%) | 3.1% (−13.7%–19.9%) | 18.9% (15.2%–22.7%) | 3.6% (1.3%–8.5%) |
| <100 | 14.5% (10.7%–18.5%) | 33.9% (25.9%–41.9%) | 35.0% (18.9%–51.2%) | 15.6% (11.7%–19.5%) | 1.6% (−3.5%–6.7%) |
| Maximum number of quadrants involved in first 48 hours | |||||
| One | – | – | – | 3.9% (−1.0%–8.8%) | 3.9% (−1.0%–8.8%) |
| Two | 11.3% (7.0%–15.6%) | 9.7% (−2.9%–22.4%) | 12.0% (−5.3%–29.4%) | 12.8% (8.6%–17.0%) | 2.3% (−2.7%–7.3%) |
| Three | 10.8% (6.6%–15.1%) | 20.0% (9.7%–30.2%) | 18.3% (−1.8%–38.5%) | 10.9% (6.6%–15.1%) | – |
| Four | 18.8% (15.1%–22.4%) | 36.4% (28.2%–44.6%) | 22.3% (7.0%–37.6%) | 18.7% (15.1%–22.4%) | – |
| Subphenotype | |||||
| Hypoinflammatory | 18.3% (14.4%–22.1%) | 21.3% (10.2%–32.4%) | 14.1% (1.9%–26.3%) | – | – |
| Hyperinflammatory | 19.4% (15.9%–23.0%) | 31.9% (22.4%–41.5%) | 25.9% (7.4%–44.4%) | – | – |
Our primary analysis used matching without replacement with ICU mortality as the primary outcome measure. We repeated the analysis without matching in all four models to examine how matching—and therefore selection of controls, affected AF estimates. The matched analysis was also conducted using hospital mortality (instead of ICU mortality) as the outcome measure in model 2.
AF, attributable fraction; AHRF, acute hypoxaemic respiratory failure; AHRF-UL, acute hypoxaemic respiratory failure with unilateral infiltrates only; ARDS, acute respiratory distress syndrome; ICU, intensive care unit.