Evaluating the Diagnostic Accuracy of Xpert MTB/RIF Assay in Pulmonary Tuberculosis

Pulmonary tuberculosis still remains a major communicable disease worldwide. In 2013, 9 million people developed TB and 1.5 million people died from the disease. India constitutes 24% of the total TB burden. 

Early detection of TB cases is the key to successful treatment and reduction of disease transmission. Xpert MTB/RIF, an automated cartridge-based molecular technique detects Mycobacterium tuberculosis and rifampicin resistance within two hours has been endorsed by WHO for rapid diagnosis of TB. 

Our study is the first study from India with a large sample size to evaluate the performance of Xpert MTB/RIF assay in PTB samples. The test showed an overall sensitivity and specificity of 95.7% (430/449) and 99.3% (984/990) respectively. In smear negative-culture positive cases, the test had a sensitivity of 77.7%. The sensitivity and specificity for detecting rifampicin resistance was 94.5% and 97.7% respectively with respect to culture as reference standard. However, after resolving the discrepant samples with gene sequencing, the sensitivity and specificity rose to 99.0% and 99.3% respectively. 

Hence, while solid culture still forms the foundation of TB diagnosis, Xpert MTB/RIF proposes to be a strong first line diagnostic tool for pulmonary TB cases.

Full article at: http://goo.gl/X54bXP

By:

Surendra K Sharma, Mikashmi Kohli, Raj Narayan Yadav, Jigyasa Chaubey, Dinkar Bhasin, Rohini Sharma, Binit K Singh

Department of Internal Medicine, All India Institute of Medical Sciences, New Delhi, India

Vishnubhatla Sreenivas

Department of Biostatistics, All India Institute of Medical Sciences, New Delhi, India

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Accuracy of QuantiFERON-TB Gold Test for Tuberculosis Diagnosis in Children

To evaluate the accuracy of the QuantiFERON-TB Gold assay (QFT-IT) in children with suspected active or latent TB infection (LTBI).

A retrospective study was conducted on 621 children (0–14 years old) evaluated for TB infection or disease. Following clinical assessment, children were tested with the QFT-IT assay.

Among the 140 active TB suspects, we identified 19 cases of active disease. The overall sensitivity for active TB was 87.5%, ranging from 62.5% in children 25–36 months old to 100% in children older than 49 months. The overall specificity for active TB was 93.6%. Among the 481 children tested for LTBI screening, 38 scored positive and all but 2 had at least one risk factor for TB infection. Among the 26 children with indeterminate results, bacterial, viral or fungal pneumonia were later diagnosed in 11 (42.3%) cases and non-TB related extra-pulmonary infections in 12 (46.1%).

Our results indicate that the children's response to QFT-IT associates to active TB and risk factors for LTBI. Moreover, we show that mitogen response is also found in children of 1 year of age, providing support for QFT-IT use also in young children.

Below:  Quantitative response to QuantiFeron TB Gold-In Tube in relationship to age

Full article at: http://goo.gl/D8TAhz

By: 

Michela Sali, Pamela D’Alfonso, Antonella Zumbo, Giovanni Fadda, Maurizio Sanguinetti, Giovanni Delogu

Institute of Microbiology, Università Cattolica del Sacro Cuore, Rome, Italy

Danilo Buonsenso, Piero Valentini

Institute of Pediatrics, Università Cattolica del Sacro Cuore, Rome, Italy

Delia Goletti

Translational Research Unit, Department of Epidemiology and Preclinical Research, "Lazzaro Spallanzani" National Institute for Infectious Diseases (INMI), IRCCS, Rome, Italy

  

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