The certainty of the evidence in oral health has not improved according to GRADE: a meta-epidemiological study

Objective: The aim of this meta-epidemiological study was to provide an update of the certainty of the evidence in oral health by using the GRADE rating reported in oral health Cochrane systematic reviews (CSR). Study design and setting: All interventional oral health CSR published between 2003-2021 were sourced. Study characteristics were extracted at the level of the CSR and the outcome/meta-analysis. One-hundred-five CSR were eligible and analysed. Results: Almost a third of CSR (n = 67) were excluded as a GRADE rating was not available. The most prevalent type of primary studies included in the CSR were randomized studies (93.4%) and the most used measure of effect was the risk ratio (67.3%). Overall, the certainty of the evidence according to the GRADE rating for all examined outcomes was very low/low (88%). The two most common reasons for downgrading the confidence in the evidence were study limitations (Risk of bias) and imprecision. The odds of moderate/high vs. low/very low-GRADE rating are higher for the primary compared to the secondary outcomes after adjusting for year and number of trials (OR 2.49; 95% CI: 1.09, 5.65; P=0.02). Per year (2010-2021 period) the odds of moderate/high vs. low/very low-GRADE rating decrease (OR 0.73; 95% CI: 0.60, 0.90; P=0.01), and as the number of trials per comparison increase the odds of moderate/high vs. low/very low GRADE rating increase (OR 1.13; 95% CI: 1.01, 1.25; P=0.001). Conclusions: The certainty of the evidence in oral health when assessed with the GRADE rating remains predominantly low or very low. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

This meta-epidemiological study aimed to evaluate the certainty of evidence in oral health by examining the GRADE ratings in Cochrane systematic reviews. The results showed that the certainty of evidence for all outcomes examined was primarily rated as very low or low. Factors such as study limitations and imprecision were the main reasons for downgrading confidence in the evidence. Overall, the study found that the odds of achieving a moderate/high GRADE rating were higher for primary outcomes compared to secondary outcomes, and that the certainty of evidence tended to decrease over the years 2010-2021.