The lower detection limit of the assay has been estimated at 131 CFU/mL hence. Good diagnostic performance has also been shown for TB lymphadenitis. A 2013 Cochrane review by Steingart et al summarized several evaluations of Xpert MTB/RIF, demonstrating high overall sensitivity and specificity, albeit mostly conducted in individuals with suspected pulmonary TB. This gene is probed with molecular beacons to detect rifampicin resistance mutations which can be used as surrogate markers for multidrug-resistant TB (MDR-TB). This assay is an all inclusive molecular test that uses real-time polymerase chain reaction (PCR) to amplify a Mtb-specific sequence of the RNA polymerase gene ( rpoB). In December 2010, the WHO approved a new molecular assay-based test, Xpert MTB/RIF, for the diagnosis of TB in HIV-positive individuals. In resource-limited settings, mycobacterial culture therefore mainly has a role for surveillance and for cases with suspected drug resistance. Furthermore, culture results may be affected by antibiotic therapy, as well as storage and transport conditions. However, widespread use of culture is compromised by protracted result delivery, high upfront cost and strict requirement of advanced biosafety precautions.
Mycobacterial culture is generally considered to have the highest sensitivity for detection of Mycobacterium tuberculosis (Mtb), and is generally used for reference in evaluation of alternative techniques it is also the only method that can give information on antibiotic sensitivity patterns. In HIV-positive individuals the performance of sputum smear microscopy is unsatisfactory the sensitivity of this technique in HIV-positive individuals starting ART in South Africa was 22% and 26% using one and two samples, respectively. In most settings, especially at primary health care level, the century-old acid fast bacilli (AFB) smear microscopy is currently the only available method to diagnose TB. Although the overall sensitivity of the current algorithm is 79%, its specificity is estimated at 50%, indicating that a majority of patients identified will need further investigations to ascertain their TB status. The World Health Organization (WHO) recommends regular symptom screening for TB for HIV-positive individuals in TB-endemic settings. In addition, isoniazid preventive therapy (IPT) may be inadvertently administered to patients with active TB. Delayed diagnosis of TB increases the risk both of mortality and of immune reconstitution inflammatory syndrome, in patients receiving ART, and is also associated with TB transmission in health facilities and in the community. Atypical disease manifestations and lack of suitable diagnostic tools contribute to suboptimal TB case finding –. Studies from South Africa, Uganda and Tanzania have shown unrecognized active TB in 7–31% of patients starting ART –. The recent achievements in mortality reduction in HIV-positive individuals through the scale up of antiretroviral therapy (ART) in sub-Saharan Africa have been dented by a high occurrence of TB, which remains the leading cause of death. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Ĭompeting interests: The authors have declared that no competing interests exist. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.įunding: The Swedish International Development Cooperation Agency (SIDA), the Swedish Civil Contingency Agency (MSB) and the Swedish Medical Society have provided funding for this study. Received: JAccepted: NovemPublished: January 22, 2014Ĭopyright: © 2014 Balcha et al. PLoS ONE 9(1):Įditor: Delmiro Fernandez-Reyes, National Institute of Medical Research, United Kingdom (2014) Intensified Tuberculosis Case-Finding in HIV-Positive Adults Managed at Ethiopian Health Centers: Diagnostic Yield of Xpert MTB/RIF Compared with Smear Microscopy and Liquid Culture. Citation: Balcha TT, Sturegård E, Winqvist N, Skogmar S, Reepalu A, Jemal ZH, et al.
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