Introduction

Hepatitis A virus (HAV) is a member of the Hepatovirus genus of Picornaviridae family. It is a single-stranded RNA virus with a non-enveloped icosahedral structure. HAV has only one serotype. It has some properties of enteroviruses such as stability and resistance to inactivation at low pH levels and at a temperature of -20 0C (1,2).

Acute hepatitis A infection shows different clinical courses ranging from asymptomatic infection to fulminant disease. Diagnosis of hepatitis A is based on demonstration of specific antibodies against HAV using ELISA method (2,3).

Since HAV is transmitted by the fecal-oral route, its prevalence is naturally in line with economic development of the region. Although its prevalence has been decreased in developed countries along with improved hygiene conditions, it leads to substantial rates of morbidity and economic loss in developing countries. In Turkey, the prevalence of anti-HAV antibody positivity in adult age-group is reported between 89% and 100% (3,4). The HAV seroprevalence rate in pediatric patients under 10 years of age is lower than 40%. The HAV seroprevalence increases depending on the age (5,6).

The present study aimed to investigate the seroprevalence of hepatitis A among pediatric and adult age groups admitted to our hospital, which serves as a training and research hospital.

Materials and Methods

The presence of anti-HAV IgM and IgG antibodies was explored in serum samples sent to our laboratory with a prediagnosis of hepatitis A between June 2012 and July 2013, and positive samples were retrospectively investigated according to age groups. A total of 6697 patients were included in the study, 3537 of them were investigated for anti-HAV IgM and 5363 were investigated for anti-HAV IgG. Only one of anti-HAV IgM and IgG tests were studied in 4492 patients. Both anti-HAV IgM and IgG were tested in a total of 2205 patients. Pediatric patients were divided into seven groups (0-1, 2-3, 4-5, 6-7, 8-9, 10-11, 12-13) and adult patients were divided into three groups (14-19, 20-29, >30).

Blood samples obtained for anti-HAV IgM and IgG antibody screening were centrifuged at 10.000 rpm for 15 min and then examined by the chemiluminescent microparticle immunoassay (CMIA) and electrochemiluminescence immunoassay (ECLIA) within 2 hours at the latest using Cobas® 4000 e411 (Roche, Germany) and Architect i2000SR (Abbott Diagnostics, Germany) analyzers. The statistical difference between the age groups was analyzed by comparison of ratios using Z test, and a p value of <0.05 was considered significant.

Results

Over the course of the study period, the results of 6697 patients were examined in terms of anti-HAV antibodies. Anti-HAV IgM antibody was evaluated in 3537 patients and positivity rate was found to be 2.9% in all age groups, whereas anti-HAV IgG antibody was analyzed in 5363 patients and the positivity rate was found to be 89.9% in all age groups. A total of 207 patients were found negative in both anti-HAV IgM and IgG test results. It was observed that IgM antibody increased after the age of 1 year and peaked at the age of 6-7 years; it gradually decreased thereafter and regressed below 1% after the age of 14 years. While the positivity rate of IgG antibody was about 34% at the age of 0-1 year, it regressed to 27% in the next age group and increased thereafter in line with age. Rates of anti-HAV IgM and IgG antibody positivity are presented in Table 1 and Figure 1.

Discussion

HAV is frequently encountered from early childhood in under-developed and developing countries and maintains its importance as an important public health problem. Particularly, small children with asymptomatic infection are responsible for intra-familial transmission. Transmission is more common in the incubation period when the individual is still asymptomatic. Environments with crowded living conditions such as hospitals, schools, nurseries, preschools, and continuing care centers are important places for the development of outbreaks (7).

While the prevalence of anti-HAV antibody is low in Japan, Australia, New Zealand, Canada, America and most of the European countries, many Latin American, Asian and Middle Eastern countries have high prevalence, although average seroprevalence rates are declining (8). The world is divided into three endemicity regions as high, moderate and low, according to the detection rate of HAV. Turkey is in the moderate endemicity region with a seroprevalence of 40-70% in 10-year age group and 90% over the age of 15 years. Some epidemiological studies in Turkey have reported that seropositivity is declining (4,5).

Demirpençe et al. (9) reported anti-HAV IgG antibody positivity to be 93.9% in outpatients in Batman; whereas, Turhan et al. (10) reported anti-HAV IgG antibody positivity rate of 81.1% in Hatay and expressed that positivity increased with age. Kurt et al. (11) found the overall anti-HAV IgG antibody positivity to be 79.3% in healthy individuals in Ankara and observed that positivity was over 96% in individuals older than 25 years of age. Özen and colleagues (12) reported IgG antibody positivity rate of 25.9% within the age range of 2-16 years in Malatya province and determined that the rate of positivity was higher among school children. Similar with this study, Arvas et al. (13) found the rate of IgM antibody to be 18.1% in children of 0-18-year-age group and reported that the highest rates were detected in 6-12-year-age group, which is the primary school-age group. Kalem et al. (14) carried out a study in Konya province and reported the rate of anti-HAV IgM antibody to be 2.89% and that of anti-HAV IgG antibody to be 77%. They found that anti-HAV IgM antibody positivity was significantly higher in patients living in the periphery of Konya as compared to those living in the city center. Karslıgil and colleagues (15) found anti-HAV IgM and IgG antibody positivity rate of 19.4% and 74.6%, respectively in Gaziantep. In addition, they demonstrated that anti-HAV IgM antibody positivity rate was the highest between the ages of 5 and 14 years. Tekay (16) reported anti-HAV IgM and IgG antibody positivity to be 5% and 68% in Hakkari, which is close to our province. This lower anti-HAV IgM antibody rate as compared to the other studies was attributed to the higher socioeconomic level of the individuals that were able to go to hospital.

In the present study, anti HAV IgM and IgG antibody positivity rates were found to be 2.9% and 89.9%, respectively in all age groups. It was observed that IgM antibody positivity was higher within the age range of 2-11 years, with the highest rates found in the age range of 6-7 years. This was attributed to the crowded family life and high number of school-age children. It was observed that IgG antibody positivity increases in line with age. Moreover, it was concluded that higher rates observed in 0-1-year-age group as compared to 2-3-year-age group might have resulted from the antibodies transferred from the mother. Considering all age groups, it appears that the results of the present study are consistent with the above mentioned literature information.

Conclusions

The present study found high anti HAV IgM antibody positivity rates, particularly in the pediatric age group. Considering that the prevalence of HAV shows parallelism with age, socio-economic status, crowded family life, higher number of school-age children and the level of development and decreases with the increase in socio-economic level, necessary public health measures must be carried out meticulously.