Puranjay Saha, Royani Saha
BACKGROUND Tuberculosis is a chronic multi system granulomatous disease with a predilection for the respiratory system. Traditional diagnostic protocols include history, chest x-ray and sputum collection and staining for acid fast bacilli along with culture in conventional media. These processes are time consuming and labour intensive. WHO recommends the use of Cartridge Based Nucleic Acid Amplification Testing (CBNAAT) using the Gene Xpert MTB/RIF apparatus which is a comparatively rapid PCR based test. MATERIALS AND METHODS In the present study, sputum and tissue samples from 1299 patients were taken and smear preparations were stained for acid fast bacilli. Subsequently, the samples were subjected to CBNAAT testing for both the presence of mycobacterium tuberculosis as well as rifampicin resistance, which is a marker for INH resistance as well. Rifampicin resistant tuberculosis is thus labelled as multi drug resistant tuberculosis (MDR TB). RESULTS In the results of the study, mycobacterium tuberculosis (MTB) was found in 1275 cases, Rifampicin sensitivity was found in 1095 cases, rifampicin resistance in 176 cases and indeterminate results in 4 cases. In 122 cases of the present study, CBNAAT has detected mycobacterium tuberculosis (MTB) where the cases were smear negative. On the other hand, 109 smear positive cases have been declared MTB negative by CBNAAT testing. 26 cases showed error, invalid test and no results. In 4 cases though MTB was detected, rifampicin resistance testing showed indeterminate results. CONCLUSION CBNAAT technology may be used as the standard diagnostic tool for tuberculosis. However for disputed cases, referral systems must be in place for mycobacterial culture and drug testing at reference laboratories.
