Original Research

Evaluation of the Ogawa-Kudoh method for tuberculosis isolation in two health units in Mozambique

Carla M. Madeira, Khalide I. Azam, Daisy N. Sato, Celso Khosa, Nilesh Bhatt, Sofia O. Viegas
African Journal of Laboratory Medicine | Vol 9, No 1 | a929 | DOI: https://doi.org/10.4102/ajlm.v9i1.929 | © 2020 Carla M. Madeira, Khalide I. Azam, Daisy N. Sato, Celso Khosa, Nilesh Bhatt, Sofia O. Viegas | This work is licensed under CC Attribution 4.0
Submitted: 30 October 2018 | Published: 20 July 2020

About the author(s)

Carla M. Madeira, National Tuberculosis Reference Laboratory, Instituto Nacional de Saúde, Marracuene, Mozambique
Khalide I. Azam, National Tuberculosis Reference Laboratory, Instituto Nacional de Saúde, Marracuene, Mozambique
Daisy N. Sato, American Society for Microbiology, São Paulo, Brazil
Celso Khosa, Centro de Investigação e Treino em Saúde da Polana Caniço, Instituto Nacional de Saúde, Marracuene, Mozambique
Nilesh Bhatt, Centro de Investigação e Treino em Saúde da Polana Caniço, Instituto Nacional de Saúde, Marracuene, Mozambique
Sofia O. Viegas, Department of the Laboratory Network and Reference Services, Instituto Nacional de Saúde, Marracuene, Mozambique


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Abstract

Background: Mozambique is among the highest tuberculosis, tuberculosis–HIV and multidrug-resistant-tuberculosis burden countries. Although molecular technologies are available in-country, mycobacterial isolation through culture remains an important tool for tuberculosis diagnostics and drug susceptibility testing.

Objective: We evaluated the use of the Ogawa-Kudoh (OK) mycobacterial culture, a simple technique, to isolate Mycobacterium tuberculosis in two health units, in Maputo City, Mozambique.

Methods: From May to December 2014, 122 patient samples were collected in Chamanculo General Hospital and Polana Caniço General Hospital. The specimens were first tested in the health units using the OK method and afterwards shipped to the National Tuberculosis Reference Laboratory for mycobacterial culture using the NALC-NaOH-Citrate (NALC) decontamination method followed by inoculation in Lowenstein Jensen (LJ) solid media as the reference standard.

Results: Among 107 samples with valid results, 98 (91.6%) had concordant results in both methods; 9 (8.4%) had discordant results. The contamination rate was 4.1% (5/122) for the OK and 9.0% (11/122) for the NALC/LJ methods. The sensitivity of OK was 80% (95% confident interval [CI]: 51.4–94.7) and the specificity was 94% (95% CI: 85.8–97.3). The degree of agreement between both methods was moderate (Kappa: 0.68; 95% CI: 0.48–0.89).

Conclusion: The OK method showed satisfactory sensitivity and specificity. The method also had a lower contamination rate when compared to the NALC/LJ. Similar to other studies in resource-limited settings, our findings showed that the OK method can effectively be implemented in settings with limited laboratory capacity to isolate tuberculosis bacteria by culture for further testing.


Keywords

Ogawa-Kudoh; mycobacterial culture; tuberculosis diagnostics; Mozambique; laboratory

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