Considering the disease burden of liver cancer and its low survival rate 
, early diagnosis of liver cancer through screening is important in reducing the corresponding cost and mortality. The results of the present study showed that only 39.6% of our study sample, made up of individuals at high risk for liver cancer aged 20 or more ever got liver cancer screening in their lifetime, 12.3% reported regular screening (i.e., screening in the previous 6 months), and 14.6% reported complete screening (i.e., screening by both abdominal ultrasonography and serum AFP testing). We found that older age, moderate self-reported health status, and awareness of HBV infection status were associated with increased regular liver cancer screening rate, compared with never-screening. Being female, having a lower household income, working in a routine or manual occupation, and unawareness of HBV infection status were associated with decreased complete screening rate, and people aged 40–69 years had higher complete liver cancer rate.
Previous studies conducted in Korea showed that the lifetime liver cancer screening rate among individuals at high risk for the disease increased from 31.8% in 2004 to 54.3% in 2011 
. These studies targeted high-risk individuals such as chronic HBV or HCV carriers, or liver cirrhosis patients aged 40 years or more. When we restricted our analyses to those aged 40 or more, the lifetime liver cancer screening rate was 43.8% (data not shown). These results including our study were lower than the results of other countries 
. Although receiving liver cancer screening every 6 months for high-risk individuals have been recommended considering tumor doubling time 
, only 12.3% of our study sample reported regular liver cancer screening. Our results fell between those of the study conducted by Noh et al., which reported a 6% liver cancer screening rate within the previous 6 months 
, and the 22.9% in the study by Park et al 
. However, all of these results are much lower than those from China in which 23.5% or 40.6% got regular screening 
Older age was associated with both increased regular and complete liver cancer screening. In Korea, the National Cancer Screening Program, an organized screening program for gastric, liver, colorectal, breast, and cervical cancers provided by government, provided liver cancer screening using both abdominal ultrasonography and serum AFP testing every 6 months for those aged 40 years old or over who are HBsAg-positive, anti-HCV positive, or have liver cirrhosis either for free, or with a 10% deductible 
. This organized screening program may contribute to the higher regular and complete screening rates we observed in the older age groups compared with those less than 40 years old.
A previous study showed that HBV or HCV carriers who were aware of their infection status got abdominal ultrasonography more often during their lifetime 
, whereas in our study they received regular and complete liver cancer screening more often. Perceived risk has been positively associated with cancer screening 
and therefore, it could be suggested that large a proportion of high risk group did not get appropriate liver cancer screening because they did not know that they were in high risk of liver cancer. In our study 77% of HBV carriers (464 of 604) were unaware of their infection status. This is much lower than a previous study in Korea, which reported that only one-fourth of HBV carriers were unaware of their infection status 
. However, that study population was composed of participants of an opportunistic cancer screening program conducted on the basis of personal preference in a single general hospital and they were considered to be concerned about their health status more.
The relationship between self-rated health status and cancer screening is controversial. Some have reported that a better self-rated health status was associated with increased cancer screening attendance 
, while others suggested that those with better self-rated health status were less likely to attend cancer screening 
. In our results, moderate self-reported health status was associated with increased regular liver cancer screening but poor self-rated health status did not show significant results compared with good self-rated health status. However, the trend showed marginal significance showing that poorer self-rated health status increased the regular screening rate (P-trend 0.071). However, poorer self-rated health status increased the irregular and incomplete screening rate compared to never-screening.
Compared with males, females were less likely to get complete liver cancer screening. One possible explanation could be that males have more opportunities to attend organization- and government-supported screening in the workplace. Our results regarding the association between household income and complete liver cancer screening were in accordance with those from previous studies on screening behavior for other cancer types in general population. Higher household income was associated with a higher cancer screening rate for colorectal, gastric, breast, and cervical cancer screening 
. Occupation reflected socioeconomic status in our study, and affected the complete liver cancer screening rate.
This study has several limitations. First, as all the information was measured by self-report in health surveys, therefore we cannot rule out the possibility of information bias. Indeed, self-reported information on liver cancer screening and screening method was not matched to medical records. However, previous studies have shown that self-reported cancer screening history is reliable, and agrees well with medical records 
. Second, we restricted high-risk individuals to those with positive serum assays for HBsAg because we did not measure HCV antibodies in serum, although people who were anti-HCV-positive were included in the target population of the National Cancer Screening Program in Korea. Considering that the target population of the National Cancer Screening Program in Korea included 4.6% of anti-HCV carriers, the study population might not represent the entire high-risk group for liver cancer, although it was representative of total HBV carriers.
Despite of these limitations, this study has several strengths. The results are based on a large, nationally representative sample of high-risk individuals. Second, to our knowledge, this is the first study to investigate factors associated with regularity and completeness of liver cancer screening in individuals at high risk for liver cancer and we expect that the results might provide new opportunities to explore liver cancer screening behavior and practice in this population.
As Korea remains an area of intermediate HBV prevalence, and that the burden of liver cancer is especially great among individuals with low socioeconomic status 
, efforts to increase the liver cancer screening rate, following recommended methods (both abdominal ultrasonography and serum AFP testing) and intervals (6 months) for those at high risk are necessary. In conclusion, our finding indicate that the lifetime screening rate, regular screening rate, and complete screening rate for liver cancer were much less suboptimal, and age and awareness of HBV infection status were positively associated with both regular and complete liver cancer screening in our study sample of individuals at high risk for liver cancer. In addition, other sociodemographic factors such as sex, household income, and occupation were associated with regular and complete liver cancer screening. The strategies for increasing liver cancer screening should be different from those for other cancers, which target the general population. Considering that those unaware of their HBV infection status got regular and complete liver cancer screening much less often, efforts should be made not only to decrease sociodemographic disparities, but also to better identify the high-risk population. Although the National Cancer Screening Program for liver cancer offers HBsAg and anti-HCV testing for free to Medical Aid Program recipients, the participation rates were low. Therefore, increasing the awareness of guidelines for liver cancer screening to large proportion of population in Korea might be needed. Further studies on the enhancement of liver cancer screening rate targeting high risk group are warranted.