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Table 6 Silica exposure controlled for silicosis and tuberculosis (adjusted and crude GIV), GradePro schema

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

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   Pooled relative risk (95% CI)  
All
5
Observational Not serious Not serious Not serious Not serious None 13,617 1.92 (1.36, 2.73) LOW
Low/intermediate
2
Observational Not serious not serious Not serious Not serious None 6879 2.75 (1.70, 4.45) LOW
High
3
Observational Not serious not serious Not serious Not serious None 6738 1.66 (1.04, 2.66) LOW
  1. GIV generic inverse variance, CI confidence interval
  2. a Risk of bias: Not downgraded. The overall risk of bias was low across four out of five studies measuring silica exposure. Non-differential exposure misclassification arising from use of proxies for silica exposure is likely to reduce rather than increase any true effect
  3. b Inconsistency: Not downgraded. Overall I2 reduced from 59% to zero after adjustment for study design by omission of the two case-control studies (one of which had a high risk of bias). Low/ intermediate TB countries): I2 = 0%. High TB countries: I2 was reduced from 73% to zero after adjusting for study design by omission of the one case-control study
  4. c Indirectness: Not downgraded as exposure metrics were well established proxies of silica exposure, the exact disease of interest was studied, and the studies covered miners in South Africa, foundry workers in Denmark and a variety of silica exposure occupations in Iran
  5. d Imprecision: Not downgraded. Large sample sizes and 95% confidence intervals exclude the null, i.e. sufficient precision