Title: Diagnostic Yield of Cartridge Based Nucleic Acid Amplification Test (CBNAAT) in Pulmonary Tuberculosis with People Living with HIV (PLHIV) Compared to Sputum Microscopy
Authors: Dr Srujana Akella, Dr V.N. Raju, M.D, Dr Gayatri M.D, Dr V. Prathyush M.D, Dr Preethi, M.D
DOI: https://dx.doi.org/10.18535/jmscr/v7i11.82
Abstract
Introduction: Tuberculosis is a highly infectious disease which is caused by Mycobacterium tuberculosis. Tuberculosis is the most common opportunistic infection in PLHIV, and the risk of death in HIV-TB co-infected individuals are high .In 2017, among HIV-negative people, estimated deaths caused by TB were 1.3 million (range, 1.2–1.4 million) and there were an additional 3,00,000 deaths from TB (range, 2,66,000–3,35,000) among HIV-positive people. we have taken up the study of comparing detection of mycobacterial tuberculosis bacilli in sputum by Xpert/RIF and method in fluroscent smear pulmonary tuberculosis and rifampicin resistance with a special focus on PLHIV
Aims and Objectives
- To compare the sputum microscopy and cartridge based nucleic acid amplification test (CBNAAT) in diagnosing
pulmonary tuberculosis with people living with HIV (PLHIV).
- To determine whether there is any correlation between CD4 counts in terms of detection with these two techniques among plhiv patients.
Materials and Methods: One hundred PLHIV patients with age >18 years with symptoms suggestive of tuberculosis who met the criteria were selected. All patients included in the study underwent a detailed history and clinical examination. CD4 lymphocyte counts of all the patients were determined by flow cytometry. Two Sputum samples were collected at least 1ml for each patient, in 2 sterile containers. One was sent for AFB smear examination under fluorescent microscopy. One sputum sample of 1 ml was collected in a sterile falcon container and was analyzed by CBNAAT on Xpert® MTB/RIF
manufactured by Cepheid, endorsed by WHO (2010).Data analysis was done using Microsoft Excel software. Diagnostic yield of sputum microscopy and CBNAAT were compared with McNemar test.
Observations and Results
- Total 100 PLHIV patients with presumptive PTB were included in the
Sputum microscopy detected 21 cases and sputum for CBNAAT detected 52 cases. Smear-positive CBNAAT negative cases were 4. A total number of PLHIV patients with pulmonary tuberculosis were 56.
- CD4 cell count upto 100 cells/ml was seen in 16 patients and PTB was detected in 11(68%) cases by CBNAAT. In 19 patients with CD4 COUNT 101- 200 cells/ml, PTB was detected in 14(73.68%) cases by CBNAAT COUNT >500 cells/ml, PTB was detected in 7(26.92%) cases by CBNAAT. Mean CD4 count was 355.84±281.25 cells/ml. CBNAAT positive and sputum microscopy positive cases were CBNAAT negative and sputum microscopy positive cases were 4.CBNAAT positive and sputum microscopy negative were 35.P-value was 0.0031 (<0.05) which was significant. Out of 52 CBNAAT detected cases, 48 were rifampicin sensitive and 4 were rifampicin resistant.
Conclusion: CBNAAT is to be indicated as a primary diagnostic test in PLHIV with presumptive TB.CBNAAT detects pulmonary TB in PLHIV with greater efficacy than sputum microscopy, also helping in early diagnosis in less than 2 hours. It also detects rifampicin resistance with high specificity and can be used for screening for MDR-TB so that early therapy can be started, thus decreasing the incidence of MDR-TB.
Keywords: PLHIV, sputum microscopy, CBNAAT, Pulmonary tuberculosis, CD4 count.
