title: Evaluation of the Xpert® MTB/RIF assay and microscopy for the diagnosis of Mycobacterium tuberculosis in Namibia.
abstract: BACKGROUND
  Tuberculosis (TB) kills approximately two million people and infects around nine million worldwide annually. Its proper management, especially in resource-limited settings, has been hindered by the lack of rapid and easy-to-use diagnostic tests. Sputum smear microscopy remains the cheapest, readily available diagnostic method but it only identifies less than half of the patients with a HIV/TB co-infection because the bacilli would have disseminated from the lungs to other areas of the body. The fully automated Xpert® MTB/RIF assay is a promising innovation for diagnosing TB and detecting resistance to rifampicin. This study aimed to evaluate the use of Xpert® MTB/RIF assay and microscopy in the diagnosis of Mycobacterium tuberculosis in Namibia, by determining the disease's epidemiology and calculating the proportion of cases infected just with TB and those with a resistance to rifampicin among the total suspected cases of TB in the country.
  
  
  METHODS
  This retrospective study analysed TB cases that were diagnosed using both the Xpert® MTB/RIF assay and microscopy. Data were collected from patient records from the Meditech laboratory information system of the Namibia Institute of Pathology for the time period of July 2012-April 2013. Data from 13 regions were collected.
  
  
  RESULTS
  The total number of specimens collected from patients with symptoms of pulmonary TB was 1 842. Of these, 594 (32.20%) were found to be positive for MTB by Xpert® MTB/RIF assay, out of which 443 (24.05%) were also found to be positive by microscopy. The remainder was negative. The male patients were more resistant to rifampicin when compared to the female patients.
  
  
  CONCLUSIONS
  Tuberculosis is widely distributed throughout Namibia, with slightly more males infected than females. Most TB patients are also co-infected with HIV. Both microscopy and Xpert® MTB/RIF assay are crucial for the diagnosis of TB in the country. Screening diagnostic efforts should focus on the sexually active HIV positive male population who could be the source of more RIF-resistant TB than females to prevent its spread.
authors.affiliation: Department of Health Sciences, School of Health and Applied Sciences, Namibia University of Science and Technology, Private Bag 13388, Windhoek, Namibia. rmavenyengwa@yahoo.com.|Department of Medical Microbiology, University of Zimbabwe College of Health Sciences, P. O. Box A178, Harare, Zimbabwe. rmavenyengwa@yahoo.com.
authors.forename: Rooyen T
authors.initials: RT
authors.lastname: Mavenyengwa
authors.affiliation: Department of Health Sciences, School of Health and Applied Sciences, Namibia University of Science and Technology, Private Bag 13388, Windhoek, Namibia.
authors.forename: Emma
authors.initials: E
authors.lastname: Shaduka
authors.affiliation: Department of Mathematics and Statistics, Namibia University of Science and Technology, Private Bag 13388, Windhoek, Namibia.
authors.forename: Innocent
authors.initials: I
authors.lastname: Maposa
mesh_terms: D000904:Antibiotics, Antitubercular / Q000494:pharmacology; D060085:Coinfection / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology / Q000821:virology; D003955:Diagnostic Tests, Routine / Q000379:methods*; D024881:Drug Resistance, Bacterial; D006678:HIV / Q000302:isolation & purification; D015658:HIV Infections / Q000150:complications / Q000175:diagnosis / Q000453:epidemiology / Q000821:virology; D006801:Humans; D009169:Mycobacterium tuberculosis / Q000302:isolation & purification*; D009276:Namibia / Q000453:epidemiology; D012189:Retrospective Studies; D012293:Rifampin / Q000494:pharmacology*; D012680:Sensitivity and Specificity; D014397:Tuberculosis, Pulmonary / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology / Q000382:microbiology
chemical_list: D000904:Antibiotics, Antitubercular; D012293:Rifampin
keywords: Diagnostic tests; Microscopy; Namibia; Rifampicin; Tuberculosis; Xpert® MTB/RIF assay