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Page 4 of 10 Chen et al. Hepatoma Res 2018;4:4 I http://dx.doi.org/10.20517/2394-5079.2017.50

Figure 2. Flow chart for enrollment of participants into Qidong hepatitis B virus infection cohort. HBsAg: hepatitis B surface antigen

migration rate of the local population older than their 30s is low, attrition from the QBC was rare. The total
response rate as of the end of February 2017 was 99.6%.

To construct a bio-bank to facilitate future research, blood samples were collected both at baseline and
during every follow-up. Plasma and white blood cells were divided into aliquots and stored under appropriate
conditions at the Shanghai Cancer Institute, the Qidong Liver Cancer Institute, and the John Hopkins
University. Their coding system was the same as preserved in the Qidong Liver Cancer Institute. As of
February 2017, a total of 23,815 plasma samples, 17,581 urine samples and 17,581 white blood cells from
cohort members were acquired and properly stored. There were 1453, 1163, 815 and 144 participants donating
serial plasma samples of more than 5, 10, 15 and 20 years’ duration, respectively. Apart from body fluid and
blood samples, 35 tumor tissue samples and adjacent non-tumor liver tissues from PLC incident cases within
the QBC were well preserved in liquid nitrogen as well.

WHAT HAS BEEN MEASURED?
Questionnaires
At the baseline survey between 1991 and 1992 certified doctors and nurses with the aid of trained local
physicians conducted the personal interviews by asking information on socio-demographic characteristics
and past medical history. A standardized, structured questionnaire completed through face to face interviews
was administrated in 1998 and covered all participants. The questions included socio-demographic data,
dietary habits, type of drinking water, consumption of alcohol, tea, and tobacco, past medical history and
present medical condition, family history of cancer, menstrual and reproductive history (females only),
and vaccination history. In 2012, an updated questionnaire was implemented, and some new variables such
as history of diabetes and use of antiviral therapy in members of the HBV exposed sub-cohort were also
documented. Brief items and variables of both structured questionnaires were illustrated in Table 1.

Physical examination and blood tests
During each follow-up, height, weight, and blood pressure were measured and recorded. Laboratory tests
for HBsAg, ALT, and AFP and upper abdominal ultrasonic exam were also performed at least once a year
between 1992 and 2017. Antibody to hepatitis C virus (HCV) was measured in 2009 to determine the rate
of co-infection of HBV and HCV. In the 2009 and 2012 follow-ups, HBV serum markers, including HBsAg,