Systematic review and meta-analysis of esophageal cancer in Africa: Epidemiology, risk factors, management and outcomes

Table 3 Quality of the 12 case control studies included in the meta-analyses of risk factors for esophageal cancer

Quality variable	Quality variable categories	Number of studies	Proportion (column %)
Representativeness of sampling procedures used in each study	Non-probability	12	100.0
	Probability	0
Response rate	Above 80%	10	83.3
	Between 60% and 80%	2
	Not reported	0
Validity of measurement methods for risk factors	Face to face interview	12	100.0
	Self-administered questionnaire
Bias in the measurement of the esophageal cancer	Histology	10	83.3
	Endoscopy	1
	Not reported	1
Control for important confounders	Yes	11	91.7
	Not reported	1
Final score (mean across the items)			91.7