Utility of cartridge based nucleic acid amplification test in the diagnosis of extra pulmonary tuberculosis

Background: Tuberculosis is one of the top 10 cause of death globally. Extra-pulmonary tuberculosis is an important clinical problem. Extra-pulmonary tuberculosis range from 30%-53% in India. Diagnosis of extra-pulmonary tuberculosis is still challenging despite many investigations. World Health Organization recommends Gene-Xpert Mycobacterium Tuberculosis/Rifampicin (Cartridge Based Nucleic Acid Amplification Test-CBNAAT) over conventional tests for diagnosis of extra-pulmonary tuberculosis which permits rapid tuberculosis diagnosis through detection of the genetic sequence of DNA of mycobacterium tuberculosis and simultaneous identification of a majority of the mutations that confirm Rifampicin resistance which is highly predictive of multi-drug resistant tuberculosis.Methods: Study was carried out over a period of one year. Patients with suggestive of extra-pulmonary tuberculosis were included in study. Diagnosis of extra-pulmonary tuberculosis carried out by clinical, radiological, biochemical analysis, cytological, bacteriological confirmation. Based on mycobacterium tuberculosis result, the study population were divided into ‘Mycobacterium Tuberculosis detected’ and ‘Mycobacterium Tuberculosis not detected’ groups. Mycobacterium Tuberculosis detected group was further divided into ‘Rifampicin resistant’ and ‘Rifampicin sensitive’.Results: Total 220 patients were included. Among extra-pulmonary tuberculosis, there were 83.64% were pleural fluid. 65.91% patients where be <45 years of age. Mostly patients were from rural areas and illiterate. Diabetes Mellitus found as the most common co-morbidities. CB-NAAT was able to detect mycobacterium tuberculosis in 35% (77) extra-pulmonary samples, out of which 6 were rifampicin resistant. Out of 184 samples of pleural fluid, 53 were rifampicin sensitive and 4 were found rifampicin resistant.Conclusions: CB-NAAT has to be endorsed in every health care centres as the test gives rapid result and also detection of rifampicin resistance which is the major concern for every clinician.