Journal Article

Use of T Cell-Based Diagnosis of Tuberculosis Infection to Optimize Interpretation of Tuberculin Skin Testing for Child Tuberculosis Contacts

Mustafa Bakir, Davinder P. S. Dosanjh, Jonathan J. Deeks, Ahmet Soysal, Kerry A. Millington, Serpil Efe, Yasemin Aslan, Dilek Polat, Nihat Kodalli, Aysegul Yagci, Isil Barlan, Nerin Bahceciler, Emel E. Demiralp and Ajit Lalvani

in Clinical Infectious Diseases

Published on behalf of Infectious Diseases Society of America

Volume 48, issue 3, pages 302-312
Published in print February 2009 | ISSN: 1058-4838
Published online February 2009 | e-ISSN: 1537-6591 | DOI: http://dx.doi.org/10.1086/595847
Use of T Cell-Based Diagnosis of Tuberculosis Infection to Optimize Interpretation of Tuberculin Skin Testing for Child Tuberculosis Contacts

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Background. Treatment of recent tuberculosis infection in children aged <2 years is essential, because of high risk of progression to disease, but diagnosis is hindered by the inaccuracy of the tuberculin skin test (TST). More-accurate T cell–based tests of infection could enhance diagnosis by optimizing interpretation of the TST results.

Methods. A total of 979 child tuberculosis contacts in Istanbul underwent the TST and enzyme-linked immunospot assay. Using enzyme-linked immunospot test results as a reference standard, we assessed the effect of age and bacille Calmette-Guérin (BCG) vaccination on the sensitivity and specificity of the TST, and we computed the optimal TST cutoff points, using receiver operating characteristic curves.

Results. With a TST cutoff point of ⩾10 mm, the sensitivity of the TST was 66% for children aged <2 years, which was lower than that for older children (P=.006). Specificity was 75% for BCG-vaccinated children, compared with 92% for unvaccinated children (P=.001). Optimal cutoff points improved TST specificity for children with 1 BCG scar, with little loss of sensitivity. Despite the use of optimal cutoff points, TST sensitivity remained <70% for children aged <2 years, specificity remained <87% for BCG-vaccinated children aged ⩾2 years, and overall accuracy was low for children with >1 BCG scar.

Conclusions. Negative results of the TST cannot exclude tuberculosis infection for child tuberculosis contacts aged <2 years, which supports the use of preventive therapy regardless of the TST results for this age group. In children aged ⩾2 years, the accuracy of the TST can be improved by adjustment of cutoff points for BCG-vaccinated children but remains poor for children with >1 BCG scar. This methodology can define optimal TST cutoff points for diagnosis of tuberculosis infection tailored to target populations.

Journal Article.  5995 words.  Illustrated.

Subjects: Infectious Diseases ; Immunology ; Public Health and Epidemiology ; Microbiology

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