Table 2.
Comparison of estimates of the PAF of ICU death due to VAP as obtained by four different competing risk analyses
| 10 Days since ICU Admission | 30 Days since ICU Admission | 60 Days since ICU Admission | |
|---|---|---|---|
| Patients with VAP infection, n (%) | 160 (5.9) | 208 (7.6) | 210 (7.7) |
| VAP-free ICU deaths, n (%) | 316 (11.6) | 452 (16.6) | 471 (17.3) |
| ICU deaths, n (%) | 340 (12.5) | 513 (18.9) | 540 (19.9) |
| Approach 1: competing risk analysis restricted to patients who remain VAP-free until end of follow-up | |||
| Estimated deaths had VAP been eradicated, n (%)* | 342.4 (12.6) | 489.8 (18.0) | 510.4 (18.8) |
| Estimated PAF, % (95% CI) | −0.7 (−3.6 to 0.2) | 4.5 (1.8 to 7.4) | 5.5 (2.9 to 8.2) |
| Approach 2: competing risk analysis that treats VAP acquisition as a competing event | |||
| Estimated deaths had VAP been eradicated, n (%)* | 335.8 (12.3) | 489.4 (18.0) | 510.4 (18.8) |
| Estimated PAF, % (95% CI) | 1.3 (−1.5 to 3.7) | 4.6 (1.9 to 7.4) | 5.5 (2.9 to 8.2) |
| Approach 3: competing risk analysis that treats VAP acquisition as a censoring event | |||
| Estimated deaths had VAP been eradicated, n (%)* | 331.6 (12.2) | 488.6 (18.0) | 512.2 (18.8) |
| Estimated PAF, % (95% CI) | 2.5 (−0.3 to 5.1) | 4.8 (2.0 to 7.7) | 5.2 (2.6 to 7.8) |
| Approach 4: competing risk analysis that adjusts for time-dependent confounding by IP weighting | |||
| Estimated deaths had VAP been eradicated, n (%)* | 333.8 (12.3) | 496.2 (18.2) | 520.1 (19.1) |
| Estimated PAF, % (95% CI) | 1.8 (−1.1 to 4.8) | 3.3 (0.2 to 6.3) | 3.7 (0.8 to 6.6) |
Definition of abbreviations: CI = confidence interval; ICU = intensive care unit; IP = inverse probability; PAF = population-attributable fraction; VAP = ventilator-associated pneumonia.
The counterfactual risk of ICU death by Day t had VAP been prevented for all is estimated by weighing each VAP-free ICU death before or at Day t by a factor that captures the degree of depletion of patients with VAP infection by the end of study follow-up (approach 1), by Day t (approach 2), by the corresponding time of ICU death (approach 3), or with a similar observed covariate history by the corresponding time of ICU death (approach 4). See the online supplement for more details.