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Table 1 GRADE quality of evidence for the association between modern housing and clinical malaria outcomes

From: The evidence for improving housing to reduce malaria: a systematic review and meta-analysis

Outcomes Summary of findings Quality of the evidence Overall quality of the evidence (GRADE)
Relative effect (95 % CI) No. participants (studies) Risk of bias Inconsistency Indirectness Imprecision Publication bias
Malaria infection: Case–control, cross-sectional and cohort studies (crude OR) OR 0°46 (0°33–0°62) 22,700 (9 studies) Serious1 No serious inconsistency2 No serious indirectness3 No serious imprecision4 Undetected5 LOW1,2,3,4,5,6,7 due to risk of bias, large effect
Malaria infection: Case–control, cross-sectional and cohort studies (adjusted OR) OR 0°53 (0°42–0°67) 3949 (5 studies) Serious1 No serious inconsistency8 No serious indirectness9 No serious imprecision4 Undetected5 VERY LOW1,4,5,7,8,9,10 due to risk of bias
Clinical malaria: Case–control and cross-sectional studies (crude OR) OR 0°32 (0°19–0°54) 357 (1 study) Serious1 No serious inconsistency11 Serious12 No serious imprecision4 Undetected13 VERY LOW1,4,6,7,11,12,13 due to risk of bias, indirectness, large effect
Clinical malaria: Case–control and cross-sectional studies (adjusted OR) OR 0°35 (0°20–0°62) 357 (1 study) Serious1 No serious inconsistency11 Serious12 No serious imprecision4 Undetected13 VERY LOW1,4,6,7,11,12,13 due to risk of bias, indirectness, large effect
Clinical malaria: Cohort studies (crude RR) RR 0°22 (0°14–0°35) 1653 (3 studies) Serious1 No serious inconsistency14 Serious15 No serious imprecision4 Undetected13 LOW1,4,7,13,14,15,16 due to risk of bias, indirectness, large effect
Clinical malaria: Cohort studies (adjusted RR) RR 0°55 (0°36–0°84) 2237 (3 studies) Serious1 No serious inconsistency17 Serious15 No serious imprecision4 Undetected13 VERY LOW1,4,13,15,17,18 due to risk of bias, indirectness
  1. Patient or population: People of all ages living in malaria-endemic regions
  2. Settings: East Timor, Egypt, Ethiopia, Greece, Malawi, Mexico, Sri Lanka, Tanzania, Thailand, Uganda and Yemen
  3. Intervention: modern (versus traditional) housing
  4. GRADE Working Group grades of evidence: High quality: Further research is very unlikely to change confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on confidence in the estimate of effect and is likely to change the estimate. Very low quality: The estimate is very uncertain
  5. 1Downgraded by 1 for serious risk of bias: All studies were non-randomized and observational
  6. 2No serious inconsistency: All nine studies observed a protective effect of modern housing, compared to traditional housing. The smallest effect was a 28 % reduction in the odds of malaria infection
  7. 3No serious indirectness: These nine studies were conducted in a variety of sites, both urban and rural, in settings across sub-Saharan Africa, Asia and Europe. The findings are generalizable elsewhere
  8. 4No serious imprecision: The overall effect was statistically significant and clinically important
  9. 5Publication bias not detected: Egger's test for bias in crude results found no evidence funnel plot asymmetry (bias coefficient 0.52, 95 % CI −1.61 – 2.65, p = 0.60)
  10. 6Upgraded by 1 for large effect: OR lies within the range 0 to 0.5
  11. 7No evidence that residual confounding would reduce the demonstrated effect: no significant difference between crude and adjusted effects
  12. 8No serious inconsistency: All five studies observed a protective effect of modern housing, compared to traditional housing. The smallest effect was a 27 % reduction in the odds of malaria infection
  13. 9No serious indirectness: These five studies were conducted in a variety of sites, both urban and rural, in sub-Saharan Africa and Asia. The findings are generalizable elsewhere
  14. 10No large effect: Odds Ratio does not fall into the range 0 to 0.5
  15. 11No serious inconsistency: only one study
  16. 12Downgraded by 1 for indirectness: only one study was included, which was conducted in rural Mexico and the findings may not be generalizable elsewhere
  17. 13Publication bias not detected: insufficient studies to construct funnel plots
  18. 14No serious inconsistency: all three studies observed a protective effect of modern housing, compared to traditional housing. The smallest effect was a 53 % reduction in incidence of clinical malaria
  19. 15Downgraded by 1 for serious indirectness: all studies were conducted in rural sub-Saharan Africa. The results may not be generalizable to other settings
  20. 16Upgraded by 2 for very large effect: Rate ratio and 95 % confidence intervals lie within the range 0 to 0°5
  21. 17No serious inconsistency: all three studies observed a protective effect of modern housing, compared to traditional housing. The smallest effect was a 25 % reduction in the incidence of clinical malaria
  22. 18No large effect: RR does not fall into the range 0 to 0°5