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Afr J Lab Med. 2018 Jun 4;7(1):690. doi: 10.4102/ajlm.v7i1.690. eCollection 2018.

Low-cost diagnostic test for susceptible and drug-resistant tuberculosis in rural Malawi.

Author information

Department of Microbiology, College of Arts and Sciences, The Ohio State University, Columbus, Ohio, United States.
Child Legacy International, Msundwe, Lilongwe, Malawi.
Department of Infectious Diseases, School of Medicine, University of North Carolina Project, Tidziwe Centre, Lilongwe, Malawi.
Department of Microbial Infection and Immunity, College of Medicine, The Ohio State University, Columbus, Ohio, United States.
District Tuberculosis Control Office, Ministry of Health, Lilongwe, Malawi.
Department of Community Health, College of Medicine, Blantyre, Malawi.
Department of Pediatrics, Obstetrics, Gynecology and Preventive Medicine, Autonomous University of Barcelona, Barcelona, Spain.
College of Public Health, The Ohio State University, Columbus, Ohio, United States.
Center for Biostatistics, College of Medicine, The Ohio State University, Columbus, Ohio, United States.
The Wellcome Centre for Clinical Tropical Medicine, Imperial College of London, London, United Kingdom.
Department of Microbiology, Cayetano Heredia University, Lima, Peru.
Division of Infectious Diseases, Department of Internal Medicine, College of Medicine, The Ohio State University, Columbus, Ohio, United States.



Rural settings where molecular tuberculosis diagnostics are not currently available need easy-to-use tests that do not require additional processing or equipment. While acid-fast bacilli (AFB) smear is the most common and often only tuberculosis diagnosis test performed in rural settings, it is labour intensive, has less-than-ideal sensitivity, and cannot assess tuberculosis drug susceptibility patterns.


The objective of this study was to determine the feasibility of a multidrug-resistant (MDR) or extensively drug-resistant (XDR)-tuberculosis coloured agar-based culture test (tuberculosis CX-test), which can detect Mycobacterium tuberculosis growth and evaluate for drug susceptibility to isoniazid, rifampicin and a fluoroquinolone (i.e. ciprofloxacin) in approximately 14 days.


In this study, 101 participants were enrolled who presented to a rural health clinic in central Malawi. They were suspected of having active pulmonary tuberculosis. Participants provided demographic and clinical data and submitted sputum samples for tuberculosis testing using the AFB smear and tuberculosis CX-test.


The results showed a high level of concordance between the AFB smear (12 positive) and tuberculosis CX-test (13 positive); only one sample presented discordant results, with the molecular GeneXpert MTB/RIF® test confirming the tuberculosis CX-test results. The average time to a positive tuberculosis CX-test was 10 days. Of the positive samples, the tuberculosis CX-test detected no cases of drug resistance, which was later confirmed by the GeneXpert MTB/RIF®.


These findings demonstrate that the tuberculosis CX-test could be a reliable low-cost diagnostic method for active pulmonary tuberculosis in high tuberculosis burden rural areas.

Conflict of interest statement

The authors declare that they have no financial or personal relationships which may have inappropriately influenced them in writing this article.

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