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INTRODUCTION
The hepatitis C virus (HCV) infection and hepatitis B virus (HBV) are the leading causes of chronic liver disease and liver cancer in Korea. Many studies on the prevalence of HBV or HCV infection have been performed using non-representative samples or small samples from a selected population. Regarding the prevalence of the HBV, the National Health and Nutrition Survey (NHNS) in 1998 included some serologic markers for HBV infection (1). Unfortunately, there is no population-based serologic study that has estimated the prevalence of a HCV infection. In this study, we investigated the pooled estimates of HCV prevalence using data from 15 reports. In recent years, the pooled-analysis using published reports has been increasing for epidemiological study (2).
MATERIALS AND METHODS
Identification of studies
Publications on the HCV antibody and its relationship with epidemiology (prevalence, risk factors) were obtained from PubMed and KoreaMed (www.pubmed.gov and www.koreamed.org) (1990-2004) and by checking the reference lists to find other reports. These reports cover the prevalence of anti-HCV in the general population, the distribution of risk factors, and the transmission route of the HCV infection. Reference lists of publications were examined to identify studies. The data from 15 reports were included in this paper. These reports had more than 500 subjects and the number of subjects that were positive for HCV according to age and gender were listed.
Data extraction
The following information was extracted: the study area, study year, method of the anti-HCV test, the distribution of study subjects according to age and gender (if available) from 15 reports on the general population (Table 2).
Statistical methods
We studied 146,561 subjects from 15 publications and 1,275 subjects were positive for HCV. HCV prevalence was estimated by multiple logistic regression analysis and is expressed as a percentage according to age and gender. The HCV prevalence by time and age was estimated with the model, logit (p)=β0+β1 time+β2 age, where p is probability that the subject was positive for HCV, time variable was categorized by 1990-1994, 1995-2000 and age variable was categorized by 40-49, 50-59, 60+ yr. The HCV prevalence by time and gender was estimated with the model logit (p)=β0+β1 time+β2 gender, where gender variable was categorized by male and female.
The pooled estimates of the prevalence of HCV were calculated as a truncated prevalence among adults 40 yr and older due to the rarity of cases in those under 40 yr of age. The pooled estimates were calculated by standardizing the estimated HCV prevalence in the Korean population (Resident registration population from Korea National Statistical Office) by time and age.
RESULTS
Seroprevalence of anti-HCV
In the 1990s, the overall anti-HCV prevalence was approximately 0.68-3.54% among health check-up middle-aged examinees (age 40 yr and over) and 0.42-1.45% among healthy people with a normal ALT level (Table 1). In the pooled analysis, the age-standardized prevalence truncated to those 40 yr and older was 1.68% (95% CI 1.51-1.86) (Table 3). During 1990-1994, the prevalence was 2.90% (95% CI 2.53-3.33), and was different from 1.39% (95% CI: 1.24-1.55) during 1995-2000. Some of the published data showed that the prevalence of anti-HCV in males was similar to that in females. However, a pooled estimate of the HCV prevalence in males (0.77%, 95% CI: 0.72-0.83) was significantly lower than in females (1.06%, 95% CI: 0.97-1.16) (Table 3).
DISCUSSION
The important goal of this study was to calculate a quantitative pooled estimate of the prevalence of HCV. Even though there were limitations in the publication bias and the heterogeneity between the studies in the pooled-analysis, our estimates of the prevalence are believed to be conservative.
The overall HBsAg prevalence was 5% in the NHNS (Korea National Health & Nutrition Survey, 2002). HBV is by far a more important risk factor for hepatocellular carcinoma in Korea. A HCV infection shows a stronger association with hepatocellular carcinoma in elderly patients (3). In Korea, the surveillance program for anti-HCV positive people 40 yr and older was introduced by the Ministry of Health and Welfare and the National Cancer Center in 2003.
There are few papers that have reported the prevalence among children and young adults. The prevalence of anti-HCV in children (6-11 yr old) was 0.81% (17/2,080) in Seoul in 1995 (4) and 0.4% (5/1,350) among young adults (16-24 yr old) (5).
Most HCV infected persons in Korea are elderly. However, more attention should be paid to whether new infections occur in groups besides the elderly. Some of the published data showed a similar prevalence of the anti-HCV in males and females, but two reports indicated that the anti-HCV prevalence among females was higher than that among males in the rural population (6, 7). These two reports are from the same area. Therefore, the regional variation in the prevalence of the HCV should be clarified in future studies.
Most of the published data showed that the frequency of anti-HCV increased with age. The high prevalence of anti-HCV among older persons is most likely due to a cohort effect of the risk of acquiring a HCV infection being higher in the distant past than currently. Because HCV is rarely transmitted by a blood transfusion in Korea since the introduction of the HCV antibody test to screen blood donors (April 1991), the risk of HCV exposure among blood recipients has decreased. Therefore, an evaluation of the behavioral risk factors other than blood transfusions is important in terms of the transmission of the HCV infection.
Although the anti-HCV positive prevalence has reduced in recent years, the HCV RNA positive rates must be closely monitored in the future to determine the actual risk of HCV infection and further study for reduction of the anti-HCV positive prevalence is needed.
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