Mantoux reaction survey conducted in the northern region of Saudi Arabia.

A nationwide epidemiological survey is under way to assess the prevalence of tuberculosis infection in the inhabitants of Saudi Arabia. The assessment tools include the Mantoux test and culturing of sputum samples obtained from inhabitants of the five regions of the Kingdom. The study population has been selected using a proportional-to-population-size method with cluster sampling and urban/rural stratification. We report the results of the Mantoux test for the Northern Region, where 1340 subjects were screened. Only 4% of the non BCG-vaccinated children had a positive reaction (tuberculosis index = TI) which identifies the region as a middle prevalence country (2-14%), and indicates the need for better detection and treatment of open cases of tuberculosis in the community. The TI rose steeply with age to 58% in the 65+-year age group, which denotes the existence of a large pool of infected but healthy subjects who are liable to suffer active disease. The TI was higher males and in those doing manual work, but was not statistically influenced by nationality (Saudis versun non-Saudis), place of residence, or level of education. Our findings support the view that a positive tuberculin reaction in a child aged 5 to 14 years who has been vaccinated with bacillus Calmette-Guerin (BCG) should be attributed to infection with Mycobacterium tuberculosis and not BCG. This conclusion is based on our finding that only 5% of the children int he group of vaccinated subjects has a positive Mantoux reaction, 5% had an intermediate reaction (5 to 9 mm induration), and 90% had a negative reaction (0 to 4 mm induration).