Table 3.
Results of meta-analyses
| Type of analysis | Subgroup | Random effect model (odds ratio and 95% confidence interval) | Heterogeneity | |
|---|---|---|---|---|
| I2 | p value | |||
| Primary outcome meta-analysis: adjusted survival to discharge or to 30 days after OHCA | None | 1.01 [0.93; 1.11]–PI [0.76; 1.35] | 87% | < 0.01 |
| Secondary outcome meta-analysis: unadjusted survival to discharge or to 30 days after OHCA | None | 0.68 [0.62; 0.74]–PI [0.43–1.05] | 97% | < 0.01 |
| Secondary outcome meta-analysis: unadjusted neurological intact survival | None | 0.56 [0.49; 0.66]–PI [0.32; 0.98] | 95% | < 0.01 |
| Secondary outcome meta-analysis: adjusted neurological intact survival | None | 0.96 [0.83; 1.10]–PI [0.63; 1.46] | 84% | < 0.001 |
| Subgroup analysis by quality of variables of adjustment (as defined in the manuscript) | Strong variables (17 studies) | 1.05 [0.98; 1.12]–PI [0.82; 1.34] | 80% | < 0.001 |
| Medium variables (3 studies) | 0.84 [0.68; 1.04]–PI [0.12; 6.07] | 32% | 0.23 | |
| Weak variables (1 study) | 0.88 [0.71; 1.09] | Not applicable | ||
| Subgroup analysis by geographical location | Asia (5 studies) | 0.94 [0.84; 1.06]–PI [0.63; 1.41] | 85% | < 0.01 |
| North America (7 studies) | 0.98 [0.88; 1.09]–PI [0.71; 1.34] | 88% | < 0.01 | |
| Europe (7 studies) | 1.10 [0.97; 1.25]–PI [0.79; 1.53] | 45% | 0.09 | |
| Oceania (2 studies) | 1.16 [0.93; 1.43] | 0% | 0.54 | |
| Subgroup analysis by OHCA etiology | Cardiac etiology (9 studies) | 0.99 [0.86; 1.14]–PI [0.64; 1.55] | 77% | < 0.001 |
| All etiologies (12 studies) | 1.02 [0.95; 1.11]–PI [0.79; 1.32] | 90% | < 0.001 | |
| Subgroup analysis by type of cohort and number of centres | National databases (8 studies) | 0.95 [0.87; 1.04]–PI [0.71; 1.28] | 92% | < 0.001 |
| Local cohort from EMS (9 studies) | 1.10 [0.99; 1.22]–PI [0.82; 1.47] | 81% | < 0.001 | |
| Monocentric (3 studies) | 1.08 [0.84; 1.39]–PI [0.13; 9.19] | 5% | 0.35 | |
| International cohort from EMS (1 study) | 0.94 [0.70; 1.26] | Not applicable | ||
| Subgroup analysis by population denominator | All OHCA (15 studies) | 1.05 [0.97; 1.13]–PI [0.81; 1.35] | 81% | < 0.01 |
| Only survivors to admission (5 studies) | 0.89 [0.83; 0.96]–PI [0.74; 1.08] | 34% | 0.20 | |
| Sensitivity analysis omitting papers rated as outliers (in the Baujat plot) | None | 0.97 [0.91; 1.04]–PI [0.80; 1.17] | 55% | < 0.01 |
| Sensitivity analysis omitting papers including data of traumatic etiology for OHCA | None | 1.01 [0.90; 1.15]–PI [0.68; 1.51] | 75% | < 0.01 |
| Sensitivity analysis of papers assessed with high risk of bias | None | 1.05 [0.98; 1.12]–PI [0.82; 1.34] | 80% | < 0.01 |
OHCA out-of-hospital cardiac arrest, EMS emergency medical services
For subgroups analyses, only pooled τ2 results are presented