Table 2.
Characteristics of included studies
| Study characteristics | Number (%) |
|---|---|
| Total number full papers included | 34 (100) |
| Volume and outcome relationship all conditions | 20 (58.8) |
| Volume and outcome relationship specific conditions/procedures | 14 (41.2) |
| Country | |
| USA/Canada | 30 (88.2) |
| Japan | 2 (5.9) |
| Germany | 1 (2.9) |
| Sweden | 1 (2.9) |
| Centre type | |
| Multicentre | 33 (97) |
| Single centre | 1 (3) |
| Data sources | |
| Voluntary (STS-CHD, HCUP-KIDS, PCCC, UHC) | 19 (55.9) |
| Involuntary/registry (PHIS, NIS, OSHPD, UNOS, Texas birth defects registry) | 12 (35.3) |
| Study specific | 3 (8.8) |
| Patient population | |
| All children (0–20) | 19 (55.9) |
| Newborns and infants only | 12 (35.3) |
| Adults | 3 (8.8) |
| Outcomes measured | |
| Survival/mortality only | 25 (73.5) |
| Survival/mortality and other outcomes | 7 (20.6) |
| Other outcomes only | 2 (5.9) |
| Design | |
| Retrospective cohort | 28 (82.4) |
| Retrospective observational | 1 (2.9) |
| Cross-sectional | 3 (8.8) |
| Longitudinal | 1 (2.9) |
| RCT (data source) | 1 (2.9) |
RCT, randomised controlled trial.