Table 1.
Evidence levels for the available literature on the subject of closed incision negative pressure therapy
| EbM level | Type of study | Number of studies | Percentage of studies (%) |
|---|---|---|---|
| No level | Research reports, technical reports, editorial, guidelines | 10 | 10·0 |
| 1a | Systematic review of randomised controlled trials | 6 | 6·0 |
| 1b | Individual randomised controlled trials (with narrow confidence interval) | 2 | 2·0 |
| 1c | All‐or nothing result* | 0 | 0 |
| 2a | Systematic review (with homogeneity) of cohort studies | 2 | 2·0 |
| 2b | Individual cohort study [including low‐quality randomised controlled trials (e.g. with a follow‐up of < 80%)] | 11 | 11·0 |
| 2c | ‘Outcomes’ research, ecological study | 0 | 0 |
| 3a | Systematic review (with homogeneity) of case–control studies | 0 | 0 |
| 3b | Individual case–control studies | 18 | 18·0 |
| 4 | Case series (and poor‐quality cohort studies and case–control studies) | 20 | 20·0 |
| 5 | Expert opinion without explicit critical appraisal or based on physiology, bench research or ‘first principles’ | 31 | 31·0 |
| Total | 100 | 100·0 | |
EbM, evidence‐based medicine
*
If all patients died before the therapy was available but now some survive, or if some patients died but now all survive. Classification provided by Centre for Evidence‐Based Medicine (March 2009) 5.