Tuberculin screening aims at tracking tuberculosis infection. A one-to-three-week retest has been recommended when the tuberculin test is <10 mm in the first dose to check booster effect occurrence. The booster phenomenon occurs when the tuberculin screening is <10 mm in the first dose and after the second dose, in three weeks time, there is a >10 mm induration with an increase compared to the first dose of at least 6 mm. This study, aimed at estimating booster effect rate, involved health professionals from a University hospital in Campo Grande, a town in the Brazilian state of Mato Grosso do Sul. Among the 194 participants, 65 (33,5%) were strong PPD reactors in the first test and 129 were weak or non-reactors. They went through a second test which revelled 10 were reactors. Hence, the booster effect rate was 7,8%. In the two-step tuberculin test reactor tuberculosis infection prevalence was 38.7%. The authors concluded that identifying booster effect in tuberculin screening is important to avoid under estimated rates of tuberculosis infection. It is also important to follow up recently acquired infections and evaluate the results of tuberculin screening accurately to reduce the probability of false negative results, which would otherwise be misinterpreted as refering to recently infected health professionals.
tuberculin skin test; prevalence; health care professionals; booster phenomenon
