Utility of the Gen-Probe amplified MTD test for the tuberculosis diagnosis in formalin-fixed, paraffin-embedded histologic specimens

Abstract number: 1733_1480

Ros M., Mariscal D., Ferreros P., Combalia N., Orellana R., Vázquez J.A., Fontanals D., Torra M., Rey M.

Objective: To value the relationship among the mycobacteria culture, clinical and histopathologic findings compatible with tuberculosis (TBC) and the results of the Gen-Probe amplified MTD test (MTDT) in formalin-fixed, paraffin-embedded histologic specimens.

Methodology: The affected anatomic sites of 24 biopsies were: lymph nodes (9); skin (3); synovial (2); colon (2); lung (1); pleural (1); peritoneal (1), parotid gland (1); bone marrow (1); spleen (1); breast (1); vertebral (1). All had presence of granuloma with multinucleated giant cells and/or caseous necrosis. To detect AFB, all smears were stained by Ziehl–Neelsen (ZN). Only 9 (37.5%) of the specimens were cultured for mycobacteria. A MTDT was considered positive when the result was greater than 500.000 RLU. The clinical information of the 24 patients was reviewed and those that have received antituberculous treatment or/and grew mycobacteria in the culture were considered cases of TBC.

Results: 23 of the biopsies had chronic granulomatous inflammation and 1 caseous necrosis. Only the specimen with necrosis presented ZN positive. In 7 specimens (29.1%) MTDT was positive, clinical information was suggestive of TBC and in 3 mycobacteria grew. One patient had MTDT negative, clinical information suggestive of TBC and a positive culture. In two cases, MTDT was negative, there was no culture but they were treated as TBC. Sensibility, specificity, PPV and NPV are 70%, 100%, 100% and 82.3% respectively.

Conclusions: Considering that there are cases in which the corresponding tissues are not sent for TBC culture, the MTDT can be a useful technique for the diagnosis of TBC in formalin-fixed specimens when clinical or histopathologic suspicion exists.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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