Table 3.
Risk of bias assessment
| Author | Inclusion of a control group | Justified selection of control group | Validated statistical analysis | Validated DDE measure |
Examiner number | Examiners) blinded | Inter/ Intra examiner reliability | Risk of Bias |
|---|---|---|---|---|---|---|---|---|
|
Jagels& Sweeney 1976 |
Yes | Yes, but controls were siblings of individuals with CF and may have been carriers of the CFTR gene | No | No | 1 | Yes, but case subjects were identifiable | Unknown | High |
| Primosch 1980 | Yes | Yes | No | No | Unknown | Unknown | Unknown | High |
| Narang 2003 | Yes | Yes, but the control group contained individuals with respiratory conditions | Yes | Yes | 1 | Unknown | Unknown | Medium |
| Azevedo 2006 | Yes | Yes | No | Yes | 1 | Unknown | Unknown | Medium |
| Ferrazzano 2009 | Yes | Yes | No | Yes | 2 | Unknown | Unknown | Medium |
| Ferrazzano 2012 | Yes | Yes | No | Yes | 3 | Unknown | Yes | Medium |
| Peker 2014 | Yes | Yes | Yes | No | 1 | No | Yes | Medium |
| Collard 2016 | No | N/A | No | Yes | 1 | No | Unknown | High |
| Abu-Zahra 2019 | No | N/A | Yes | Yes | 2 | No | Yes | Medium |
| Pawlaczyk-Kamieńska 2019 | Yes | Yes | Yes | Yes | 2 | No | Yes | Medium |