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Int. Rev. Allergol. Clin. Immunol. Family Med., 2016, XXII/1: 023-027 Maximize

Int. Rev. Allergol. Clin. Immunol. Family Med., 2016, XXII/1: 023-027

Title: Assessment of annual risk of tuberculosis infection (ARTI) based on Styblo’s formula as well as on tuberculin (TST) and gamma-interferon (IGRA) tests results 

Authors: Targowski T, Płusa T. 

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03-01-2016

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SUMMARY IN POLISH & ENGLISH. FULL ARTICLE ONLY IN ENGLISH. SUMMARY

Assessment of annual risk of tuberculosis infection (ARTI) based on Styblo’s formula as well as on tuberculin (TST) and gamma-interferon (IGRA) tests results

Targowski T1, Płusa T2.

1Department of Internal Medicine, Pneumonology and Allergology, Central Clinical Hospital of the Ministry of National Defense, Military Institute of Medicine, Warsaw, Poland; 2EMC Medical Institute SA – Department of Internal Medicine and Lung Disease, Hospital st. Anna in Piaseczno, Poland

Int Rev Allergol Clin Immunol Family Med, 2016; Vol. 22, No. 1, 023

In scientific literature, discrepant annual risk of tuberculosis infection (ARTI) values, calculated based on the rate of positive tuberculin tests and on the number of sputum-smear positive test cases (indirect method), have been reported.
The aim of the study
was to evaluate which test used for diagnosing of latent tuberculosis infection (LTBI) is more useful for estimation of ARTI values.
Materials and methods
. The screening group consisted of 210 volunteers living in Warsaw area. Each participant was tested using the gamma-interferon test (QFT) and tuberculin skin test (TST). The ARTI was calculated based on Styblo’s formula, which refers to the sputum-smear positive TB incidence rate, as well as on the QFT and TST results.
Results
. 199 patients were included into the study. The mean age of subjects was 43.0 (SD 10.8) years. A positive tuberculin skin test was found in 54.8% and a positive gamma-interferon test – in 11.6% of the subjects. The ARTI, based on the positive TSTs, was 1.8% for the study group while the ARTI based on the positive QFTs was six-fold smaller. The annual risk of tuberculosis infection for the studied group, calculated indirectly based on Styblo’s formula, was 0.19%.
Conclusion
. ARTI calculated from gamma-interferon test results is comparable to the ARTI value calculated from Styblo’s formula and differs greatly from ARTI value estimated on the grounds of TSTs results. This data should be taken into account for the assessment of future epidemiological trends of tuberculosis in the communities with high incidence of positive TSTs.

Key words: annual risk of tuberculosis infection, Styblo’s formula, tuberculin test, gamma-interferon test