Diagnostic strategies in the Clínica de Tuberculosis of the Hospital General of the Centro Médico Nacional La Raza

Abstract

In order to diagnose TB infection, tuberculin skin test and interferon gamma release assay are available. The tuberculin test has a sensitivity of 99 % and a specificity of 95 %. For the detection of interferon gamma in blood there are currently two tests available: TBGold QuantiFERON-In-Tube (with a sensitivity of 0.70 and a specificity of 0.90), and T-SPOT-TB (sensitivity 0.90 and specificity 0.93). To diagnose the disease, a microscopy of direct smears for acid-fast bacilli is used if the physician is facing an extensive cavitary lung disease due to M. tuberculosis (this test has a high sensitivity: 80-90 %). The most common staining techniques used are Ziehl-Neelsen and Kinyoun, and the fluorescent technique, auramine-rhodamine. The culture is the gold standard and it has a sensitivity of 80 % and a specificity over 90 %, but the results take weeks. The nucleic acid amplification test has an overall sensitivity and specificity of 0.85 and 0.97, respectively. In the presence of a pleural effusion is necessary to perform a pleural biopsy for culture with a sensitivity of 85 % if it is percutaneous and 98 % if it was taken by thoracoscopy. The adenosine deaminase can be determined in pleural fluid with a sensitivity and specificity of 95 %.