The association between silica exposure, silicosis and tuberculosis: a systematic review and meta-analysis

BMC Public Health

Table 4 Silicosis and tuberculosis (adjusted and crude GIV), GradePro schema

Certainty assessment							No. of participants	Effect	Certainty
Country TB burden. No. of studies	Study design	Risk of bias ^a	Inconsistency ^b	Indirectness ^c	Imprecision ^d	Other considerations ^e		Pooled relative risk (95% CI)
All 8	Observational	Not serious	Not serious	Not serious	Not serious	Strong association, dose response gradient	66,982	3.65 (2.79, 4.78)	⨁⨁⨁⨁ HIGH
Low/intermediate 4	Observational	Not serious	Not serious	Not serious	Not serious	Strong association, dose response gradient	59,091	4.68 (3.22, 6.80)	⨁⨁⨁⨁HIGH
High 4	Observational	Not serious	Not serious	Not serious	No serious	Strong association, dose response gradient	7891	3.16 (2.31, 4.32)	⨁⨁⨁⨁ HIGH

GIV generic inverse variance, CI confidence interval
^a Risk of bias: Not downgraded. We used the Newcastle-Ottawa Scale for cohort and case-control studies. We explored confounding in depth and determined that although confounding was approached differently across studies, the overall risk of bias from the studies did not warrant marking down overall
^b Inconsistency: Not downgraded. Overall: I² reduced from 53% to a moderate 35% following removal of outlier [46]. Low/intermediate TB burden countries: I² reduced from 49 to 14% following omission of the outlier. High TB burden countries: I² a moderate 35%, not explained by study design
^c Indirectness: Not downgraded. Exact diseases of interest were studied, and the studies covered different industries and country populations
^d Imprecision: Not downgraded. Large sample sizes with 95% confidence intervals in the strong effect range
^e Other considerations: Large effect and dose response gradient. We marked up for large effect as the associations were strong (relative risk > 2.5 to very strong > 4), although with a wide range. While we cannot exclude the possibility that further studies in different settings might alter the overall effect estimate, the clear dose response in five studies suggests that this is unlikely

ISSN: 1471-2458