Clinical Usefulness of the Line Probe Assay for Rapid Detection of Rifampicin-resistant Tuberculosis

Hong, Sang Bum; Lim, Chae Man; Lee, Sang Do; Koh, Younsuck; Kim, Woo Sung; Kim, Dong Soon; Kim, Won Dong; Shim, Tae Sun

Abstract

BACKGROUND
RpoB gene mutations have been found in about 96-98% of rifampicin (RMP)-resistant Mycobacterium tuberculosis. Recent reports confirm that the in laboratory settings a rpoB gene mutation can be used as a surrogate marker for multi-drug resistant tuberculosis. However, its usefulness in clinical applications has not been evaluated. This study was performed to confirm whether mutation analysis of the rpoB gene of M.tuberculosis is useful in clinical settings.
METHODS
The medical records of 33 patients in whom rpoB gene analysis was conducted using an INNOLiPA Rif. TB assay (LiPA) from June, 1998, to July, 2000, at the Asan Medical Center were retrospectively reviewed in 33 patients. the clinical characteristics in addition to the drug susceptibility and LiPA results were analyzed. The drug susceptibility test was considered as a gold standard method for M/ tuberculosis susceptibility and these results were compared with those of the rpoB gene study and sequencing analysis. sequencing analysis of the rpoB gene was done in cases where there was a discrepancy between the results of the drug susceptibility and rpoB gene study.
RESULTS
The mean age and sex ratio was 42±18, and 24:9(M:F), respectively. there were 19 RMP susceptible (58%) and 14 RNP-resistant cases (42%) according to the rpoB gene study. The mean time from the request to reporting the results of the rpoB gene study was 5.2±2.6 days. The mean gap from reporting the rpoB gene study to reporting the susceptibility was 56±35 days. Twenty-eight cases (85%) showed identical results compared with the drug susceptibility results, wheres five cases (15%) showed contradictory results. When compared with the sequencing analysis, of the five cases that showed contradictory results, two had LiPA analysis errors and the remaining three were identical to the sequencing results. The rpoB gene study was of assistance in choosing the appropriate drugs in 28 cases (85%).
CONCLUSIONS
An rpoB gene study using an LiPA assay was useful in rapidly diagnosing RMP-resistant tuberculosis, which enabled a proper choice of the appropriate drugs in clinical practices. However, an LiPA assay always should be performed in conjunction with microscopy, culture, and susceptibility tests.