Frequency of latent tuberculosis infection between age groups in family members of a patient with a pulmonary tuberculosis in Iran

Given that tuberculosis infection is present in one-quarter of the world's population and is more likely to convert to tuberculosis, especially at a young age, its diagnosis and prevention is an important part of the World Health Organization's (WHO) program. The aim of this study is to evaluate the frequency of latent tuberculosis infection (LTBI) in different age groups of family members of pulmonary tuberculosis patients in two provinces of Iran with a high prevalence of tuberculosis during 18 months.

Family members of confirmed pulmonary tuberculosis patients were followed up as a retrospective and prospective study in the cities of Gorgan and Zabol at 0, 3, 12 and 18 months after the starting the study. LTBI was diagnosed by using the QuantiFERON test kit and the Tuberculin skin test (TST).

The number of LTBI cases based on QFT or TST was 354 (52.99%) in the whole study and 33.33% in children under 5 years old. Positive cases of TST, QFT and LTBI in the age group over 18 years were significantly different with 5 to 18 years and less than 5 years, while there was no significant difference between the age groups of less than 5 years and 5 to 18 years.

The results of this study showed that most cases of infection occur before the diagnosis of the index case or in the first phase of study, and there is no significant difference between the diagnosis with TST or QFT.