Nucleic acid amplification test and bronchoscopy improve the diagnostic accuracy of smear-negative tuberculosis

Abstract Introduction Tuberculosis (TB) in people living with human immunodeficiency virus (PLHIV) is difficult to diagnose due to fewer organisms in sputum and extrapulmonary samples. Sputum culture takes 4 to 8 weeks for growth of the mycobacteria. Delayed treatment for TB in PLHIV leads to increased mortality. This study evaluated cartridge-based nucleic acid amplification test (CBNAAT) as a diagnostic tool for diagnosis of pulmonary TB (PTB) and extrapulmonary TB (EPTB) in PLHIV in the second most HIV prevalent state in India and for comparing its efficacy between Ziehl–Neelsen (ZN) staining sputum smear–positive and sputum smear–negative TB. Methods This cross-sectional study was conducted in RIMS, Imphal, with 167 PLHIV patients, age 15 years or older, having signs and symptoms of TB. Appropriate samples for sputum microscopy and CBNAAT were sent. Conclusion The overall sensitivity of sputum smear for acid-fast bacillus (AFB) was found to be 30.71% and that of CBNAAT was 38.57%. Sensitivity of CBNAAT for sputum smear–positive and sputum smear–negative TB was 100 and 11.3%, respectively. Sensitivity of ZN smear for AFB of EPTB sample was 48.1% and that of CBNAAT was 59.25%. In both PTB and EPTB, CBNAAT showed an increase in diagnosis of microbiologically confirmed PTB cases by 7.8 and 11.1%, respectively, over and above the cases diagnosed by ZN smear microscopy. Rifampicin resistance was detected in five patients. We conclude that CBNAAT is a rapid test with better sensitivity in diagnosis of PTB and EPTB in PLHIV, compared with ZN smear microscopy. It detects rifampicin resistance for multidrug-resistant TB and helps in early treatment intervention.

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Early diagnosis of smear-negative childhood pulmonary tuberculosis and its substantial yield in gastric lavage/aspirates through cartridge-based nucleic acid amplification test (Xpert Mycobacterium tuberculosis/rifampicin assay)

Biomedical and Biotechnology Research Journal (BBRJ) ◽

10.4103/bbrj.bbrj_56_19 ◽

2019 ◽

Vol 3 (4) ◽

pp. 258

Author(s):

PrasantaKumar Das ◽

SomtirthaB Ganguly ◽

Bodhisatya Mandal

Keyword(s):

Mycobacterium Tuberculosis ◽

Nucleic Acid ◽

Early Diagnosis ◽

Pulmonary Tuberculosis ◽

Gastric Lavage ◽

Nucleic Acid Amplification Test ◽

Nucleic Acid Amplification ◽

Smear Negative

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1346. Ruling out TB in New York City: Are Two NAATs (Nucleic Acid Amplification Testing) Enough?

Open Forum Infectious Diseases ◽

10.1093/ofid/ofz360.1210 ◽

2019 ◽

Vol 6 (Supplement_2) ◽

pp. S487-S488

Author(s):

William G Greendyke ◽

Janett Pike ◽

Lilibeth V Andrada ◽

Krystal Balzer ◽

Thelesha Gray ◽

...

Keyword(s):

New York ◽

New York City ◽

Nucleic Acid ◽

Diagnostic Accuracy ◽

York City ◽

Median Number ◽

Nucleic Acid Amplification ◽

Pulmonary Tb ◽

Nucleic Acid Amplification Testing ◽

Smear Negative

Abstract Background Prompt diagnosis of pulmonary Mycobacterium tuberculosis (TB) infection can prevent nosocomial exposure. However, sputum smears are insensitive, and turnaround time for cultures can take weeks. Rapid diagnostics, such as nucleic acid amplification testing (NAAT), on respiratory specimens of patients suspected to have TB can improve diagnostic accuracy. Current practice at our institution is to obtain ≥ 3 NAATs in high-risk patients prior to discontinuing airborne isolation, but some studies have suggested that 2 negative NAATs may be sufficient. We conducted a retrospective study of patients at our institution diagnosed with TB. Methods The study was conducted at an academic adult hospital, an academic pediatric hospital, and a community hospital in New York City. Line lists of positive cultures for TB and positive NAATs from 2014 to mid-2018 were obtained from microbiology. Chart review was performed. Patient demographics, comorbidities, and radiographic findings were collected. Concordance between culture results and NAATs was evaluated. Incidence of inpatient TB exposure was noted. Results 82 cases of TB were found in the study period (see Figure 1). 45 cases were new inpatient diagnoses of pulmonary TB. The most common presenting symptoms were cough (69%), weight loss (49%), and fever (42%, see Table 1). 38/45 (84%) of patients were originally from a country other than the United States. 43/45 (96%) of patients had abnormal lung imaging. Cavitary disease was seen in 29%; other upper lobe disease was seen in 42%. Among smear-negative pulmonary TB cases, NAAT was positive in 11/16 (69%) of patients. Within this subgroup, the sensitivity of one NAAT was 41% when compared with culture. In smear-negative, NAAT-positive patients, NAATs were fully concordant with cultures in 4/11 patients (36%, see Table 2). The median number of positive NAATs was 1; the median number of positive cultures was 2. Five patients with pulmonary TB had negative NAATs altogether (median = 3); 2/5 resulted in TB exposure investigations after airborne precautions were discontinued following NAAT results. Overall, 13/45 (28%) of new diagnoses resulted in an exposure investigation. Conclusion Obtaining ≥ 3 NAATs in patients suspected of pulmonary TB improved diagnostic accuracy compared with obtaining 2 or fewer. Disclosures All authors: No reported disclosures.

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Role of Cartridge Based Nucleic Acid Amplification Test in Diagnosing Tuberculous Empyema Thoracis – A Study from Telangana, India

Journal of Evolution of Medical and Dental Sciences ◽

10.14260/jemds/2021/348 ◽

2021 ◽

Vol 10 (22) ◽

pp. 1680-1685

Author(s):

Gaddam Ramulu Yadav ◽

Vankayala Veena Reddy ◽

Pampana Eshwaramma ◽

Tarigopula Pramod Kumar ◽

Mandarakala Gopala Krishna Murthy ◽

...

Keyword(s):

Nucleic Acid ◽

Pleural Fluid ◽

Prospective Observational Study ◽

Drug Susceptibility ◽

Acid Fast Bacillus ◽

Nucleic Acid Amplification Test ◽

Nucleic Acid Amplification ◽

Empyema Thoracis ◽

Smear Negative

BACKGROUND The pleura is involved in pulmonary or systemic tuberculosis by various mechanisms like delayed hypersensitivity. Tuberculous empyema usually results from failure of a primary tubercular effusion to resolve and further progresses to chronic suppurative form. In tuberculous empyema, the pleural fluid is purulent, and is loaded with tuberculous organisms on direct acid-fast bacillus (AFB) smear examination and / or culture of pus. We need to assess the role of cartridge based nucleic acid amplification test (CBNAAT) in the diagnosis of tuberculous empyema. METHODS This study was a prospective observational study of all adult patients of empyema above 15 years of age, admitted in the Department of Pulmonology, over a period of 1 year, 6 months after obtaining clearance from ethical committee and proper consent from the study subjects. RESULTS A total of sixty-three (63) empyema cases were recruited and analysed further. On evaluation, we diagnosed 26 cases with tubercular aetiology (41.27 %) and remaining thirty-seven (58.73 %) cases with non-tubercular aetiology. CONCLUSIONS Pleural fluid (pus) cartridge based nucleic acid amplification test (CBNAAT) is very sensitive and provides a rapid confirmed diagnosis within 2 hrs. including drug susceptibility. In this study, sensitivity of CBNAAT in suspected tuberculous empyema patients was 88.5 % and specificity was 100 %. Pleural fluid CBNAAT is more sensitive in both pleural fluid AFB smear positive (100 %) and pleural fluid AFB smear negative (72.7 %) cases. So, pleural fluid and sputum direct AFB smear and CBNAAT should be sent in all suspected tuberculous empyema cases for early diagnosis of tuberculosis and early detection of rifampicin resistance. KEY WORDS Mycobacterium Tuberculosis, Tubercular Empyema, Pleural Fluid, CBNAAT, AFB, Anti-Tubercular Drugs

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Performance of Cartridge Based Nucleic Acid Amplification Test for the Diagnosis of Smear Negative Suspected Tuberculosis - A Study from a Teaching Hospital in Thrissur, Kerala, India

Journal of Evolution of Medical and Dental Sciences ◽

10.14260/jemds/2021/238 ◽

2021 ◽

Vol 10 (16) ◽

pp. 1114-1118

Author(s):

Anupama Sethumadhavan ◽

Kavitha Paul Konikkara ◽

Davis Paul

Keyword(s):

Nucleic Acid ◽

Predictive Value ◽

Gold Standard ◽

Sputum Sample ◽

False Negative ◽

Nucleic Acid Amplification Test ◽

Nucleic Acid Amplification ◽

World Health ◽

Gold Standard Method ◽

Smear Negative

BACKGROUND In India, everyday more than 6000 people develop tuberculosis (TB) and more than 600 people die of TB (2 death every 5 minutes).1 World Health Organization (WHO) has recently endorsed cartridge based nucleic acid amplification test (CBNAAT) which has the potential to lead a revolution in the diagnosis of tuberculosis. This study intends to assess the performance of CBNAAT for the diagnosis of suspected smear negative pulmonary and extra pulmonary tuberculosis. METHODS The cross-sectional study was carried out in Department of Microbiology, Government Medical College, Thrissur, Kerala, India. CBNAAT was done in district tuberculosis center, Thrissur. The study was done from December 2016 to December 2017. Samples were sent for microscopy, culture and CBNAAT. RESULTS A total of 250 patients were evaluated. Majority of the specimens collected were sputum (61.2 %) followed by bronchial wash (17.6 %). Culture was positive in 48 specimens. CBNAAT was positive in 58 specimens. Both culture and CBNAAT were positive in 47 patients. CBNAAT was negative in 1 specimen but positive in culture test. CBNAAT detected an additional 10 samples. Taking culture as gold standard, culture positives were taken as true positives and culture negatives were taken as true negatives. Accordingly, true positive was 48, true negative was 202, false positive was 10 and false negative was 1. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were respectively 97.95 %, 95.2 %, 82.75 % and 99.5 %. CBNAAT missed out a sputum sample which was culture positive. CONCLUSIONS We found CBNAAT to be an important diagnostic modality especially in smear negative patients for early diagnosis and treatment of TB. Culture of mycobacteria is considered as a gold standard method, but it takes weeks to obtain a positive result and simultaneous detection of rifampicin resistance is not possible with this method. KEY WORDS Tuberculosis, Smear Negative TB, ZN Stain, AFB, Petroff’s Method, CBNAAT, RNTCP, Culture

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