Table 2. Odds Ratio (OR) and 95% Confidence Interval (CI) for GBC in relation to gallstone using self-reported and image verified gallstone.

Gallstone History	Self-reported gallstone history a			Self-reported gallstone using stringent definition b			Gallstone history as determined by imaging techniques c
	N(Cases | Controls)	OR(95%CI)d	Pd	N(Cases | Controls)	OR(95%CI)d	Pd	N(Cases | Controls)	OR(95%CI)e	Pe
Never	693|2455	Reference		693|2455	Reference		580|787	Reference
Ever	468|60	10.0	≤0.001	145|54	4.5	≤0.001	208|58	2.0	≤0.001
		(8.0-12.8)			(3.5-5.8)			(1.5-2.7)

Abbreviations: CI, Confidence Interval; OR, Odds ratio

^aSelf reported Gallstone; as per reported by study participant either present/not present.

^bSelf reported gallstone using stringent definition; Gallstone history was ascertained using definition of self-reported gallstone; however those gallstones diagnosed within a year prior to the date of diagnosis of gallbladder cancer for cases or within a year prior to the date of interview for controls were excluded from the analysis

^c Gall stone history as determined by imaging techniques (USG, MRI and CT scans) and using breast cancer cases as a control group.

^d Adjusted for age (continuous), education (less than 5 years schooling, ≥5 year of education), current residential region (north, north-east, central, west, south), gender, waist-to-hip ratio (continuous), tobacco chewing and tobacco smoking (yes/no), per capita per month mustard oil consumption (continuous), per capita per week fresh fish consumption (continuous)

^e Same as d; except not adjusted for gender and additionally adjusted for the number of full-term pregnancies

Missing values were excluded from analysis