[Prevalence of latent infection with Mycobacterium tuberculosis in Mazovia Region using interferon gamma release assay after stimulation with specific antigens ESAT-6 and CFP-10].

Introduction: Over 8000 cases of tuberculosis (TB) are diagnosed annually in Poland. People infected with Mycobacterium tuberculosis (MTB) have a risk of active disease around 10% during whole life, the risk is biggest in the first two years after infection. Recognizing infection before TB disease occurred enables prophylaxis against its activation and ceases transmission of infection. Knowledge about proportion of infected people in the population is crucial to predict the number of new cases of active disease.

Material And Methods: Prevalence of latent TB infection (LTBI) was tested in 700 healthy adult inhabitants of Mazovia Region in different age groups, using both tuberculin skin test (TST) and interferon gamma release assay (IGRA). Commercial test QuantiFERON(®)-TB-Gold In Tube (QFT) was used. All participants were mandatory BCG vaccinated according to Polish vaccination schedule.

Results: Twenty three per cent of participants tested positively for QFT, which was significantly less than positive results of TST (50.3%). Prevalence of positive QFT result increased with age, as does the incidence of TB in Poland. Positive QFT was most frequent in the oldest age group (48.8%) and rare in the youngest (7.1%). On the contrary, positive TST occurred more often in younger participants (45%), who rarely suffer from TB. Among people over 60, who have the highest TB incidence rate, only 33.8% tested positively with TST. Concordance between both tests was low, with kappa value 0.198. Prevalence of LTBI defined as positive QFT among health care workers (HCW) was significantly higher than in other participants (32.2% v. 20.4%, p 〈 0.01).

Conclusions: LTBI was diagnosed in 23.3% of tested population of Mazovia Region. QFT is a better tool for diagnosing LTBI as it shows positive correlation with age, the same as incidence of TB disease does. Concordance between both tests is low. Prevalence of LTBI in HCW is higher than in other participants.