Table 9.
GRADE assessment – NO2 and COPD mortality.
| Domain | Judgement | Down/Up Grade |
|---|---|---|
| Limitations in studies | 9 included studies. Risk of bias moderate because although not all studies adjusted for all confounders, exclusion of 2 high risk of bias studies did not alter summary RR. | No downgrading |
| Indirectness | All studies included the desired population, exposures and outcomes | No downgrading |
| Inconsistency | The 80% prediction interval did not include 1 (Fig. 4) | No downgrading |
| Imprecision | The number of person years in the included studies was greater than 940 000 | No downgrading |
| Publication Bias | No analysis of publication bias – too few studies (n = 9) | No downgrading |
| Large Effect Size | Summary RR = 1.02 Insufficient information on unmeasured potential confounders available | No upgrading |
| Plausible confounding towards null | Confounding direction unknown but precision may be affected | No upgrading |
| Dose-response relation | A linear dose–response relationship was assumed in all studies, 95% CI for linear RR excluded 1. 2 studies investigated the shape of the dose response relationship with no evidence to suggest non-linear | Upgrade one level |
| GRADE conclusion | No downgrade and upgrade one level | HIGH CERTAINTY EVIDENCE MEAN RR UNADUSTED FOR CO-POLLUTANTS EQUALS 1.03 PER 10μ/m3 |