Screening of serum antibodies against Mycobacterium tuberculosis by enzyme-linked immunosorbent assay (Elisa) in healthy population

: Serum samples of venous blood of healthy individuals, chosen at random from two areas of the People's Democratic republic of Yemen, were examined for the presence of IgG antibodies against mycobacterial antigen by ELISA. From the district of Aden, the capital (A), there were 214 samples (72% vaccinated by BCG, 108 men and 106 women), other 235 ones originated from mountain area Laudar Muhairas (H) (66% vaccinated, 115 men and 120 women). The overall average of acquired titres was 1:81.4 in area A, and an average of 1:102.2 was recorded in area H. There was no substantial difference in the titres level in men of the two areas (1:86.9 and 1:90 resp.), however, a significant difference was observed in women: 1:75.7 in area A and 1:114.7 in area H. In area A the titres were ranging in all age groups from 1:61 to 1:83 and the differences between age groups and between vaccinated and unvaccinated individuals were not significant. In area H the titres were generally higher (1:72 to 1:164) in the unvaccinated and 1:79 to 1:204 in the vaccinated. The differences in the unvaccinated were not of a statistical importance: in the vaccinated, the titres of the 20-29 years old (1:204.5) substantially differed from the titres obtained in other groups. The differences in titres level between the two studied areas are explained by a different epidemiological situation, namely by a higher tuberculosis infestation of some age groups in area H.