Clinical Usefulness of rpoB Gene Sequence Analysis in Lymph Node Tuberculosis.

Background: Lymph node tuberculosis (LN-TB), the most common extra-pulmonary tuberculosis, frequently shows a paradoxical response (PR) during treatment. Differential diagnosis between PR and treatment failure in LN-TB is a challenging task because drug susceptibility test (DST) is rarely performed and can be delayed due to low culture yield and a long process. The rpoB gene mutation analysis is a rapid method for detection of rifampin resistance, however, its clinical usefulness has not yet been evaluated in LN-TB. Materials and Methods: DNA extracts from LN with Mycobacterium tuberculosis polymerase chain reaction (MTB-PCR) positive were gathered and direct sequencing of rpoB gene was performed. A retrospective review of clinical and microbiologic data was performed. To evaluate the clinical usefulness of rpoB gene analysis in LN-TB, the change to a second line anti-tuberculosis regimen was used due to insufficient rifampin DST data. Results: A total of 21 DNA extracts from 25 LN-TB patients were enrolled. Three rpoB mutations (Asp516Tyr, Ser522Leu, and Ser522Ala) were observed; the Asp516Tyr mutation showed rifampin resistance, however, the DST data were not available for the other two mutations. Compared with the change to the second line regimen, the sensitivity and specificity of rpoB gene mutation analysis were 50% and 94.4%, respectively, in 20 available cases. Compared with the change to the second line regimen, the sensitivity and specificity of the rpoB gene mutation analysis were 100% and 100%, respectively, in nine available cases with PR. Conclusions: Despite development of PR, keeping the first line regimen in LNTB cases without rpoB gene mutations may be recommended. Conduct of a prospective, well designed, further study with a larger scale is warranted. [ABSTRACT FROM AUTHOR]