Background

Interferon-gamma (IFN-gamma) Release Assays (IGRA) are more specific than the tuberculosis skin test (TST) in the diagnosis of latent tuberculosis (TB) infection (LTBI). We present the performance of the QuantiFERON-TB Gold In-tube (QFT-TB) assay as diagnostic test and during follow-up of preventive TB therapy in outpatients from a TB low-endemic country.

Methods

481 persons with suspected TB infection were tested with QFT-TB. Thoracic X-ray and sputum samples were performed and a questionnaire concerning risk factors for TB was filled. Three months of isoniazid and rifampicin were given to patients with LTBI and QFT-TB tests were performed after three and 15 months.

Results

The QFT-TB test was positive in 30.8% (148/481) of the total, in 66.9% (111/166) of persons with origin from a TB endemic country, in 71.4% (20/28) previously treated for TB and in 100% (15/15) of those diagnosed with active TB with no inconclusive results. The QFT-TB test was more frequently positive in those with TST > 15 mm (47.5%) compared to TST 11-14 mm (21.3%) and TST 6-10 mm (10.5%) (p0.05).

Conclusion

Only one third of those with suspected TB infection had a positive QFT-TB test. Recent immigration from TB endemic countries and long duration of exposure are risk factors for a positive QFT-TB test and these groups should be targeted through screening. Since most patients with LTBI remained QFT-TB positive after therapy, the test could not be used to monitor the effect of preventive therapy. Prospective studies are needed in order to determine the usefulness of IGRA tests during therapy.

Anne M Dyrhol-Riise email, Gerd Gran email, Tore Wenzel-Larsen email, Bjorn Blomberg email, Christel Gill Haanshuus email and Odd Morkve email

BMC Infectious Diseases 2010, 10:57doi:10.1186/1471-2334-10-57

Artigo completo em: http://www.biomedcentral.com/content/pdf/1471-2334-10-57.pdf

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A Rede Brasileira de Pesquisa em Tuberculose (REDE-TB) é uma Organização Não Governamental (ONG) de direito privado sem fins lucrativos, preocupada em auxiliar no desenvolvimento não só de novos medicamentos, novas vacinas, novos testes diagnósticos e novas estratégias de controle de TB, mas também na validação dessas inovações tecnológicas, antes de sua comercialização no país e/ou de sua implementação nos Programa de Controle de TB no País.


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