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Predictive value of purified protein derivative in pulmonary tuberculosis in a high BCG-vaccinated population

Abstract number: P1406

Sofian M., Ramezani A., Mohraz M., Khalili H., Farahani S., Moeini L., Aghakhani A., Eshrati B., Eslamifar A., Banifazl M.

Objectives: Tuberculin skin testing (TST) is used for the identification of individuals with infection by Mycobacterium tuberculosis and other non-tuberculous mycobacteria. However, its value for the evaluation of household contacts and suspected cases of tuberculosis in populations with high BCG vaccination coverage is controversial. We aimed to determine the prevalence of tuberculosis infection and the predictive value of TST in suspicious subjects to pulmonary tuberculosis in central province of Iran.

Methods: A total of 344 suspicious subjects to tuberculosis infection (>3 weeks productive cough or a chest-x-ray suggestive for tuberculosis) with or without contact with TB cases enrolled in this study. Gold standard for tuberculosis diagnosis was smear and culture. All subjects were tested using 5 tuberculin units of purified protein derivative (PPD). The predictive value of induration was examined 48–72 hours after PPD administration.

Results: The prevalence of pulmonary tuberculosis was 20.05% in our cohort of study. Indurations of PPD geqslant R: gt-or-equal, slanted 5 mm had a positive predictive value (PPV) 33% and negative predictive value (NPV) 91%, indurations geqslant R: gt-or-equal, slanted10 mm had 34% PPV and 85% NPV and indurations geqslant R: gt-or-equal, slanted15 mm had 40% PPV and 83% NPV.

Conclusion: TST does not consider being a valuable tool for the evaluation of household contacts and suspected cases of tuberculosis in populations with high BCG vaccination coverage. The traditional induration geqslant R: gt-or-equal, slanted10 mm does not seem to be the best discriminating value between TST reactions due to infection and those due to vaccination.

The frequencies of TST cut-off diameters will be calculated and presented in the congress.

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Subject:
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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