Hepatitis B or C viral infection and risk of pancreatic cancer: A meta-analysis of observational studies

Table 1 Assessment of study quality

Ref.	Quality indicators from NOS									Score
	Selection				Comparability		Exposure/outcome
	1	2	3	4	5	6	7	8	9
Hong et al[10]	Yes	Yes	No	Yes	Yes	No	Yes	Yes	No	6
Hassan et al[11]	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	No	7
Wang et al[18]	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	No	7
Zhu et al[17]	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	No	7
Ben et al[12]	Yes	Yes	No	Yes	Yes	Yes	Yes	Yes	No	7
Berrington de Gonalez et al[9]	Yes	Yes	Yes	Yes	Yes	No	Yes	No	No	6
El-Serag et al[3]	Yes	Yes	Yes	Yes	Yes	No	Yes	Yes	Yes	8
Iloeje et al[2]	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	Yes	9

NOS: Newcastle-Ottawa quality assessment Scale. For case-control studies: (1) represents cases with independent validation; (2) cases are consecutive or representative; (3) controls are community; (4) controls have no history of pancreatic cancer; (5) study controls are comparable for age and sex; (6) study controls for any additional factor(s); (7) cases and controls have the same method of ascertainment; (8) was follow-up long enough for outcomes to occur; and (9) cases and controls have complete follow-up. For cohort studies: (1) indicates the exposed cohort study representative of the population; (2) the non exposed cohort drawn from the same population; (3) the exposure ascertainment are from secure record or structured interview; (4) the pancreatic cancer was not present at start of study; (5) cohorts are comparable for age and sex; (6) cohorts are comparable for any additional factor(s); (7) assessment of pancreatic cancer is from secure record; (8) follow-up long enough for pancreatic cancer to occur; and (9) complete follow-up.

Table 2 Characteristics of studies included in the meta-analysis

Ref.	Population	Study design	Country	Ethnicity	Case (n)	No. of control	Confirmation of HBV/HCV	Confirmation of PC	Matching criteria
Berrington de Gonalez et al[9]	Population-based	Cohort	South Korea	Asian	2194	628978	HBsAg	clinic diagnosed	Age, sex
Hong et al[10]	Hospital-based	CC	South Korea	Asian	506	1008	Anti-HCV, Anti-HBs, HBsAg	histologically confirmed	Age, sex
Hassan et al[11]	Hospital-based	CC	United States	White	476	879	Anti-HCV,Anti-HBs, Anti-HBc	pathologically confirmed	Age, sex, race
El-Serag et al[3]	Population-based	Cohort	United States	Asian	140	477	Anti-HCV, HBV	ICD-9	Age, sex
Iloeje et al[2]	Population-based	Cohort	Taiwan	Asian	48	22471	HBsAg, HBV DNA	pathologically confirmed	Age, sex, smoking, alcohol
Wang et al[18]	Hospital-based	CC	China	Asian	645	711	HBsAg, Anti-HBs, Anti-HBc	pathologically confirmed	Age, sex
Zhu et al[17]	Hospital-based	CC	China	Asian	80	77	HBsAg, Anti-HCV, Anti-HBc	pathologically confirmed	Age, sex
Ben et al[12]	Hospital-based	CC	China	Asian	943	1128	HBsAg, Anti-HBs, Anti-HBc	pathologically confirmed	Age, sex, smoking, DM, BMI

CC: Case-control study; HBV: Hepatitis B virus; HCV: Hepatitis C virus; HBsAg: Hepatitis B surface antigen; Anti-HBs: Anti-hepatitis B surface antigen; Anti-HBc: Anti-hepatitis B core antigen; Anti-HCV: Anti-hepatitis C virus; ICD-9: International Classification of Diseases, Ninth Revision; DM: Diabetes mellitus; BMI: Body mass index.

Table 3 Stratified analysis of pancreatic cancer risk by adjusted covariates

Stratifying variables	Studies (n)	OR (95%CI)	Tests for heterogeneity
			χ2	P value	I2
Adjusted for smoking
Yes	4	1.32 (1.08-1.56)	4.14	0.246	27.60%
No	2	0.99 (0.68-1.30)	0.18	0.670	0.00%
Adjusted for drinking
Yes	3	1.51 (1.17-1.85)	1.70	0.428	0.00%
No	3	1.05 (0.83-1.28)	0.53	0.766	0.00%
Adjusted for diabetes
Yes	4	1.25 (0.95-1.55)	5.22	0.156	42.50%
No	2	1.24 (0.50-1.98)	1.54	0.214	35.20%