Table 2.
Modified Downs and Black quality scoring system
| Quality indicators | Points |
|---|---|
| Reporting | |
| Is hypothesis/objectives/aim clearly described (1) | |
| Are the main outcomes to be measured clearly described in the introduction/methods (1) | |
| Are the characteristics of the study/population clearly described (1) | |
| Is the distribution of confounders among study groups clearly described and did the study adjust for those confounders (1) | |
| Are the main findings described (1) | |
| Have characteristics of patients lost to follow-up/did not complete the study been described (1) | |
| External validity | |
| Are study participants representative of entire population from which they were recruited (1) | |
| Are study participants representative of current OHCA population (1) | |
| Were those participants who were prepared to participate representative of the entire population from which they were recruited (1) | |
| Internal validity | |
| Was an attempt made to blind those measuring main outcomes of the study (1) | |
| Did the study adjust for different lengths of follow-up of participants (1) | |
| Were statistical tests used appropriate (1) | |
| Was the outcome measure accurate (1) | |
| Were the participants in the different groups recruited from the same populations (1) | |
| Were study participants in the different groups recruited over the same time period (1) | |
| Was there adequate adjustment of confounding in the analyses (1) | |
| Study design | |
| Cross sectional (0.5) | |
| Cohort prospective (2) | |
| Cohort retrospective (1) | |
| Control group (yes = 1 point, no = 0 points) | |
| Secondary/retrospective analysis (1) | |
| Sample size adequate/power analysis (yes = 1, no = 0) | |
| Total max points for study design (4 points) | |
| Total points (20) |