Prevalence of Helicobacter Pylori in Asymptomatic Population-a Pilot Serological Study in Bangladesh

Epidemiological reports reveal that H. pylon is distributed among all population in the world. The present cross-sectional study was undertaken to see the H. pylon seroprevalence rates among the asymptomatic adults, as yet reportedly no such data available in Bangladesh. Serum samples were collected from 181 consecutive subjects who attended at the health check-up centre of Bangladesh Institute of Diabetis, Endocrine and Metabolic Disorders (BIRDEM), Dhaka, during the period of August to November 1995 for medical check up. The mean age of these subjects was 30.33 years (range 20 44 yrs) . Incidentally all were male and belonged to average socioeconomic class. H. pylori specific IgG antibody level was assayed by an enzyme immunoassay kit ElAgen (Clone system). Among the 181 subjects, 166 (92%) had H. pylori specific antibodies and 15 (8%) were seronegative. No significant difference (p<0.90) in seroprevalence rates was observed among different age groups. However, the results of higher seroprevalance rates of H. pylori infection in these asymptomatic adult population of Bangladesh are consistent with that of Africa and India. J Epidemiol, 1997; 7 : 251-254.


SUBJECTS AND METHOD
The serum samples were collected from 181 consecutive healthy young male individuals who attended during the period of August to November 1995, for medical check-up at Bangladesh Institute of Research and Rehabilitation in Diabetes, Endocrine, and Metabolic Disorders (BIRDEM) Health Check Centre (BHCC) to work as immigrant worker in Malaysia.Subjects came from different parts of Bangladesh.Informations about their age and socioeconomic status were noted.After separation of serum by centrifugation, samples were stored at -2(°C before testing.The serum samples test was based on the ELISA (Enzyme Linked Immunosorbent Assay) techniques) by using an ELISA test kit, (ElAgen, Clone system S.P.A., Casalecchio Di Reno, Italy).This assay system was based on qualitative detection of lgG specific antibodies to H. pylori.The type of antigen (s) used in ElAgen kit was not detailed in the supplied instructions.The test was performed according to manufacturer's instruction.H. pylori antigens were immobilized on the wells of micro-well plate.Diluted patients serum was added to the wells.IgG antibodies specific to H. pylori, if present bind to the antigen on the micro wells.The intensity of the colour corresponds directly to the amount of antibodies present.The cut-off values of more than 15 arbitrary unit (AU) permililiter (ml) was considered as positive test.

Statistical Analysis
Statistical comparison were made with JMP software (SAS institute)24).A two sided p value of 0.05 was the criterion for statistical significance.Chi-square test was done to find any difference in prevalence of different age groups of population.

RESULTS
The baseline data is summarized in Table 1.The mean age of these subjects was 30.33 years (range 20 to 44).All were male and came from almost all the districts of Bangladesh.Study subjects were the village people, belonged to average socioeconomic class and cultivation was their sole livelihood.Among the 181 subjects, 166 (92%) had H. pylori specific IgG antibodies and 15 (8%) were seronegative (Table 2).There was no significant difference (P<0.90)observed in the prevalence of infection among different age groups.

DISCUSSION
The exact mode of transmission of bacterium is not known.Epidemiological evidences indicate that person to person transmission of H. pylori may occur either fecal -oral or oral-oral routes25).However, at present it is assumed that the most likely mode of spread would be from saliva in childhood.
Recent molecular typing studies on isolates from the United kingdom and other countries at the National Collection of Type Cultures (NC TC) showed considerable diveristy in strains from different individual, yet multiple isolates from different gastro-duodenal sites in an individual are usually identical and similarities of DNA sequence between isolates from family members indicate that some H. pylori infection are acquired in households during childhoods.Bangladesh is one of the developing countries having a reported highest point prevalence of duodenal ulcer among the population above the age of 15 years).However, population serological survey on H. pylori infection is not yet undertaken in our setting.Therefore, the present cross-sectional study on these apparently healthy individuals was undertaken to plan a future large-scale seroepidemiological survey on H. pylori in different age and socioeconomic groups.
In the testing process, qualitative assay of H. pylori antibody level was made.According to informations obtained from the manufacturer, the sensitivity and specificity for ElAgen is more than 90% in detecting H. pylori specific antibody.It compares favourably with the results of other H. pylori ELISAs in which 93.8 -100% sensitivity and 79 -90% specificity were reported 31) It is also noticed that by the age 20, all were infected.Almost similar seroprevalence rates were observed in Indian and African asymptomatic adult population 32-33).However, the present data can not be taken as an exact estimate of our population seropositivity rates, because all age, sex and socioeconomic groups were not included in the study.
Another important lacking of this assay was that the used H. pylori antigen (s) was not derived from Bangladeshi strains or isolates.Therefore, future large scale seroepidemiological study covering all age, sex and socioeconomic groups and by using our own H. pylori strain derived antigen (s) would likely to provide exact status.

Table 1 .
reports reveal that H. pylon is distributed among all population in the world.The present cross-sectional study was undertaken to see the H. pylon seroprevalence rates among the asymptomatic adults, as yet reportedly no such data available in Bangladesh.Serum samples were collected from 181 consecutive subjects who attended at the health check-up centre of Bangladesh Institute of Diabetis, Endocrine and Metabolic Disorders (BIRDEM), Dhaka, during the period of August to November 1995 for medical check up.The mean age of these subjects was 30.33 years (range 20 -44 yrs) .Incidentally all were male and belonged to average Baseline data with results. Epidemiological

Table 2 .
H. pylori seroprevalence rates in different age groups.