Genotype MTBDR plus (Hain) test in suspected MDR-TB patients

Incidence ofMDR-TB in Thailand is higher Diagnosis ofmulti-drug resistance (MDR-TB) is often delayed because of insufficient investigations. Therefore, there is a need to introduce an efficient testing method. Genotype MTBDR plus (Hain test) is a new technology of line probe assay (LPAs) In general practice, it had questionable benefit on negative and positive direct smear specimens.

Evaluate the accuracy of the Hain test as compared to the conventional culture and drug susceptibility test (DST), and evaluate the judgment of the physician on starting MDR-TB treatment after receiving the result of the Hain test.

An observational prospective study was done of 100 suspected MDR-TB patients who visited the Central Chest Institute of Thailand between September and December 2012. Ninety-four patients were included in the present study. They were assessed by direct sputum smear test, Hain test, sputum conventional culture, and drug-susceptibility test (DST) in the first visit. Followed-up treatment until cure/definite treatment were observed for definite diagnosis.

Hain tests identified 65 (69%) MTB positives, 25 (26%) MTB negatives, andfour (4%) Non-tuberculous Mycobacteria (NTM), respectively. Fourteen of 17 negative direct smear but positive Hain test samples were culture negative. We followed these 14 patients. Four patients with TB treatment were cured. Six patients received MDR treatment and improved. Two patients were misdiagnosed CA. Two patients had old scar TB lesion. Sensitivity, specificity, and accuracy ofHain test for MDR-TB detection compared to standard conventional culture were 95%, 86%, and 88%, respectively. Twelve patients were NTMculture positive. Most of them (75%) were M abscessus. Sixty-three percent of chest physicians used the result of the Hain testfor extended treatment ofstandard regimen in non-IR resistance or changing ofTB regimen. There was correlation between judgments of starting MDR-TB treatment and results of Hain test (p = 0.001), no correlation between judgments of physician and pattern (default/relapse/failure) ofprevious TB treatment history (p = 0.6), and periods oftime from first diagnosis of TB to develop suspected MDR-TB (p = 0.09) were demonstrated.

We recommend Hain test to diagnose MDR-TB in highly suspected cases, and to wait for conventional culture results to confirm NTM. Hain test has benefit in negative direct smear