Role of line probe assay in diagnosis and detection of drug resistance in Mycobacterium tuberculosis

Tuberculosis caused by Mycobacterium tuberculosis has remained a major global health problem worldwide. TB requires prolonged period of time for isolation by conventional culture methods. The emergence and spread of multi drug resistant (MDR-TB) poses great threats and challenges in controlling the infection. MDR-TB is resistant to both first line drugs rifampicin and isoniazid. PCR tests are based on targeting the mutation in rpoB, katG and inhA genes which can detect resistance to these drugs. To compare microscopy, conventional culture and Line probe assay for the detection of M. tuberculosis & detect rifampicin and isoniazid resistance using Lineprobe assay in various clinical samples. A total of 347 suspected patients of tuberculosis were included in the study. Demographic details & clinical presentation was noted. Various samples were received & processed for ZN staining, culture on LJ media and Line probe assay. Out of 347 cases, majority of cases were in the age group of 51-60 years (18.4%). Majority of the population was males (65.1%). Among suspected tuberculosis patients, cough with expectoration (55.9%) was the commonest complaint. Microscopy was positive in 17.3%, conventional culture was positive in 16.1% and line probe assay was positive in 26.2%. Out of 347, 91 were diagnosed with MTB, out of which 85.7% were sensitive to both rifampicin and isoniazid whereas 14.3% showed resistance to either rifampicin / isoniazid or both. LPA & direct microscopy are a good screening method for early diagnosis and detection of drug resistance but are not a complete replacement of conventional culture which is still a gold standard.