A STUDY ON SENSITIVITY OF CARTRIDGE BASED NUCLEIC ACID AMPLIFICATION TEST (CBNAAT) TO DETECT MYCOBACTERIUM TUBERCULOSIS IN PLEURAL FLUID AMONG SUSPECTED CASES OF TUBERCULOUS PLEURAL EFFUSION

Dr. Santanu Ghosh; Dr. Niranjan Kumar Sit; Dr. Soumya Mitra; Dr. Sourindra Nath Banerjee

Volume : VIII, Issue : VI, June - 2019

A STUDY ON SENSITIVITY OF CARTRIDGE BASED NUCLEIC ACID AMPLIFICATION TEST (CBNAAT) TO DETECT MYCOBACTERIUM TUBERCULOSIS IN PLEURAL FLUID AMONG SUSPECTED CASES OF TUBERCULOUS PLEURAL EFFUSION

Dr. Santanu Ghosh, Dr. Niranjan Kumar Sit, Dr. Soumya Mitra, Dr. Sourindra Nath Banerjee

Abstract :

Background: The incidence and prevalence of tuberculosis is very high in India. Pleural Effusion is one of the commonest manifestations of extra-pulmonary tuberculosis. Diagnosis of tuberculous pleural effusion is based mostly on indirect evidences as specific methods like smear and culture for the organism from pleural fluid lack sensitivity. Pleural biopsy helps the diagnosis as by showing tubercular granuloma. Practically, blind pleural biopsy is not done many a times and conventional culture is time consuming. CBNAAT is helpful in diagnosis of pulmonary tuberculosis from sputum samples but its efficacy to detect tuberculous bacilli in pleural fluid samples is not yet studied extensively. Considering this fact, this study was done to detect diagnostic yield of CBNAAT of pleural fluid to diagnose tuberculous pleural effusion directly in comparison to other conventional methods commonly employed by us. Method: After the approval of the Institutional Ethics Committee of Burdwan Medical College and Hospital and permission of the West Bengal University of Health Sciences (WBUHS), the present thesis work was carried out under the Department of Pulmonary Medicine, Burdwan Medical College, Burdwan between March 2017 to August 2018. After obtaining written informed consent, 106 patients were selected for the study on the basis of the predefined inclusion and exclusion criteria. All of them undergone diagnostic thoracocentesis under aseptic precautions. The aspirated pleural fluid was subjected to pathological, biochemical and microbiological analysis. The patients also had undergone routine blood investigations, sputum for AFB smear examination and relevant radiological investigations. Diagnosis of tuberculosis was established by the composite reference standard (CRS).And the patients were put on appropriate antitubercular therapy according to the RNTCP guidelines. Those who had tuberculous empyema, were treated with water- seal intercostal tube drainage along with ATT. All the data were analyzed with the help of SPSS software. A total of 106 patients studied including 65.1 % men and 34.9% women. Majority of cases of tuberculous pleural effusion occurred in the age group of 21 to 30 years comprising 33% of cases. The mean age was 34.28 years. In the present study, commonest symptoms were cough in 96(90.6%), fever 91(85.8%), shortness of eath 67(63.2%), chest pain 34 (32.1%), hemoptysis 25 (23.6%), and weight loss 18 (17%). Diabetes was the most prevalent co-morbid illness which was present in 15 (14.2%) patients. Most of the cases (97.2%) were unilateral. Among them, 38.7% cases presented as left sided and 58.5% cases were right sided pleural effusion. Only three cases (2.8%) presented as bilateral pleural effusion. Maximum cases 63 (59.4%) were moderate effusion. There were 27 (25.5%) cases of minimal and 16 (15.1%) cases of massive pleural effusion. Pleural fluid analysis showed most samples were straw coloured, mean total cell count was 1669, mean value of pleural fluid protein, sugar and ADA were 5.38 gm/dL, 72.03 mg/dL, 94.02 IU/L respectively. Pleural fluid AFB smear, CBNAAT and mycobacterial culture were positive in 15 (14.2%), 48 (45.3%) and 53 (50%) cases respectively. In the hydropneumothorax subgroup (comprising of 43 cases), pleural fluid CBNAAT was able to detect MTB in 42 cases where mycobacterial culture was positive in all the 43 cases. Taking mycobacterial culture as gold standard the sensitivity, specificity, positive predictive value and negative predictive value of CBNAAT in pleural fluid were 90.6%, 100%, 100% and 91.4% respectively. And in the hydropneumothorax population the sensitivity of pleural fluid CBNAAT was 97.7%. CONCLUSION In our study, the sensitivity, specificity, positive predictive value and negative predictive value of CBNAAT in pleural fluid were 90.6%, 100%, 100% and 91.4% respectively taking mycobacterial culture as gold standard. Our findings suggest that CBNAAT should be considered in the routine diagnostic work up in suspected cases of tuberculous pleural effusion as time factor has a very crucial role in its laboratory diagnosis. CBNAAT has also the added advantage of detection of Rifampicin resistance.