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[NAIROBI] Rapid diagnosis of drug-resistant tuberculosis is urgently needed to improve treatment outcomes in low- and middle-income countries, a study says.

Tuberculosis that no longer responds to treatment with first- and second-line medicines — drug-resistant TB — is a serious threat to achieving the Sustainable Development Goal of ending the disease by 2030 because of inadequate access to laboratory tests and appropriate treatment in many countries with high tuberculosis burden, according to the WHO.

The WHO adds that globally only 25 per cent of cases of drug-resistant tuberculosis are detected and 50 per cent cases are cured.

“Patients with drug-resistant tuberculosis rely on quick, accurate and comprehensive drug resistance testing results.”

Kathrin Zürcher, Bern University, Switzerland

“Molecular-based tests can provide results within hours or days and allow patients to be immediately started on treatment,” says Kathrin Zürcher, co-author of a study conducted in seven countries with high TB burden. “Patients with drug-resistant tuberculosis rely on quick, accurate and comprehensive drug resistance testing results and on treatment which starts immediately and is carried through to completion.”

Zürcher, a research assistant at the Institute of Social and Preventive Medicine, Bern University, Switzerland, tells SciDev.Net that molecular-based test involves analysing the DNA or genetic material of the bacterium that causes tuberculosis: Mycobacterium tuberculosis.

According to the study published in the journal Lancet Infectious Diseases this month (7 February), researchers analysed results of different tests from 634 adult patients who were treated for active TB in seven high TB burden countries: Côte d'Ivoire, Democratic Republic of the Congo, Kenya, Peru, Nigeria, South Africa and Thailand from January 2013 to December 2016. About 43 per cent of the patients were HIV-positive.

The researchers assessed test accuracy for diagnosis of any drug resistance and compared the results of the tests conducted in local laboratories with rapid tests conducted in the reference laboratory in Switzerland.

“Comparing local results with reference laboratory results for any resistance, there were 218 true and 62 false positives and 332 true and 22 false positives,” the researchers indicate in the journal.  “The study shows that the accuracy of local drug susceptibility testing to detect any resistance in high-burden countries was moderate.”

Deaths occurred in 57 per cent (eight of 14) patients with resistant strains who were under-treated.

“This is the first multicentre cohort study assessing the accuracy of drug susceptibility testing in routine settings in high-burden countries by comparing local drug susceptibility test results with those from a tuberculosis reference laboratory and assessing the impact on mortality [deaths],” the researchers add.

Zürcher says that treating drug-resistant tuberculosis is expensive, takes a long time to complete and causes a lot of discomfort for patients, and that correct diagnosis is necessary and urgently needed.

Wilson Opudo, a technical officer of HIV care and treatment, FHI360 Kenya, tells SciDev.Net that he agrees with the findings, adding that TB diagnosis is poorly done in Sub-Saharan Africa. 

“We need to employ advanced methods such as DNA sequencing in dealing with this problem,” he says. But Asaava Lucas Luvai Azaale, a tutor at Kenya-based Kenyatta University School of Pure and Applied Sciences, who conducts TB research, says that DNA sequencing requires skilled personnel.
 
He adds that in Africa there is scarcity of skilled personnel who can perform modern advanced TB tests hence the prevalence of old techniques such as the sputum culture where a patient is asked to cough deeply to bring up a mixture of saliva and mucus from the respiratory tract as test sample.
 
This piece was produced by SciDev.Net’s Sub-Saharan Africa English desk.


References

Kathrin Zürcher and others Drug susceptibility testing and mortality in patients treated for tuberculosis in high-burden countries: a multicentre cohort study (Lancet Infectious Diseases, 7 February 2019) 

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