Pattern of Drug of Resistance in Previously Treated Pulmonary Tuberculosis with Line Probe Assay

Background: Tuberculosis is global health problem known since ancient times. Drug-resistant TB has been known from the time of anti-TB drugs were first introduced for the treatment of TB. The emergence of drug resistant tuberculosis particularly MDR TB has become significant health problem worldwide and an obstacle to effective tuberculosis control. Line Probe Assay (LPA) is a Nucleic Acid Amplification Test (NAAT) which provides rapid diagnosis of R and H resistance and yield results in 72 hours.Literature on drug resistant pattern in patients who are previously treated for tuberculosis and/or suspected MDR cases with Line Probe Assay method are not studied hence this study was carried out. Aims and objectives: To know the drug resistance pattern of Rifampicin and Isoniazid in previously treated pulmonary tuberculosis cases and correlating with the demographic characteristics of patients. Methods: This study was carried out in department of Respiratory Medicine, Mahatma Gandhi Medical College and Hospital, Jaipur in AFB smear positive patients of pulmonary tuberculosis who have previously taken treatment, before reporting at OPD/IPD. The exclusion criterion was new cases of pulmonary tuberculosis. Detailed history, examination and investigations were carried out. The diagnosis of active pulmonary TB was based sputum smear examination by Ziehl - Nelson staining method. Sputum smear positive cases were subjected to line probe assay to detect resistant pattern at RNTCP accredited laboratory (SMS Medical College and Hospital, Jaipur). Results: A total of 175 previously treated sputum smear AFB positive patients of pulmonary tuberculosis were taken in this study. Out of which 141(80%) were males and 34(20%) cases were females with male : female ratio 4:1 and maximum cases (43.4%) belonged to 31-45 age group with mean age 38 years. Majority of cases belonged to rural area and lower middle class group. More than 2/3rd cases were smokers (72%) among male. Out of 175 cases, 100(57.1%) cases were drug resistant, 75(42.8%) cases were drug sensitive. Line probe assay with regard to resistant pattern was highest in grade +3 sputum (100%) followed by grade +2(98%) and grade +1(96%), while least in scanty sputum positive cases (3%). Resistance to Isoniazid (H), Rifampicin(R) and Both (H+R) were seen in 27%, 14% and 59% respectively. Half of patients (56%) out of total resistance belonged to default category of previously treated pulmonary tuberculosis cases. Resistance to H (27 cases) were 62.5% in relapse, 33.3% in default and 11% in failure cases. Out of R resistance (14 cases), 63% and 37% were in relapse and default cases. Out of 59 cases of H+R resistance 65% belonged to failure category and 20% default and 15% relapse category. Conclusion: Line Probe Assay (LPA) provides accurate and rapid diagnosis of R and H resistance and is recommended for diagnosis of DR-TB in previously treated pulmonary tuberculosis patients.