In 2022, more than 78,000 new cases of tuberculosis (TB) were reported in Brazil, with an incidence of 36.3 cases per 100,000 inhabitants. According to researchers from the Regional Prospective Observational Research for Tuberculosis (RePORT)-Brazil consortium, the country could improve the control of this infection if all patients were subjected to a sensitivity test capable of early detection of resistance not only to rifampicin, but also to isoniazid, before starting treatment. A study by the consortium published this year in Open Forum Infectious Diseases found that monoresistance to isoniazid predicted unfavorable outcomes at the national level.
Isoniazid is part of the first-choice therapeutic regimen for patients with pulmonary TB. The regimen also includes rifampicin, pyrazinamide, and ethambutol. According to Bruno Andrade, MD, PhD, Afrânio Kritski, MD, PhD, and biotechnologist Mariana Araújo Pereira, PhD, researchers from RePORT International and RePORT-Brazil, this regimen is used during the intensive phase of treatment, which usually lasts for 2 months. It is followed by a maintenance phase of another 4 months, during which isoniazid and rifampicin continue to be administered. When monoresistance to isoniazid is detected, however, the recommendation is to use a regimen containing a quinolone instead of isoniazid.
Suboptimal Sensitivity Testing
Since 2015, Brazil’s Ministry of Health has recommended sensitivity testing for all suspected TB cases. In practice, however, this approach is not carried out in the ideal manner. The three researchers told the Medscape Portuguese edition that, according to data from the National Notifiable Diseases Information System (Sinan) of the Ministry of Health, culture testing is conducted in about 30% of cases. Sensitivity testing to identify resistance to first-line drugs (rifampicin, isoniazid, ethambutol, and pyrazinamide) and second-line drugs (quinolone and amikacin) is performed in only 12% of cases.
The initiative of the RePORT-Brazil group analyzed 21,197 TB cases registered in Sinan between June 2015 and June 2019 and identified a rate of monoresistance to isoniazid of 1.4%.
For the researchers, the problem of monoresistance to isoniazid in Brazil is still underestimated. This underestimation results from the infrequent performance of culture and sensitivity testing to detect resistance to first- and second-line drugs and because the XPERT MTB RIF test, which detects only rifampicin resistance, is still used.
Resistance and Worse Outcomes
The study also showed that the frequency of unfavorable outcomes in antituberculosis treatment (death or therapeutic failure) was significantly higher among patients with monoresistance to isoniazid (9.1% vs 3.05%).
The finding serves as a warning about the importance of increasing the administration of sensitivity tests to detect resistance to drugs used in tuberculosis treatment, including isoniazid.
Testing sensitivity to rifampicin and isoniazid before starting treatment could transform tuberculosis control in Brazil, allowing for more targeted and effective treatments from the outset, said the researchers. “This not only increases the chances of successful individual treatment but also helps prevent the transmission of resistant strains and develop a more accurate understanding of drug resistance trends,” they emphasized.
They pointed out, however, that implementing this testing in the Unified Health System depends on improvements in resource allocation, coordination between the national TB program and state and municipal programs, and improvements in infrastructure and the technical staff of the Central Public Health Laboratories.
“Although the initial cost is considerable, these investments can be offset by long-term savings resulting from the reduction in the use of more expensive and prolonged treatments for resistant tuberculosis,” said the researchers.
This story was translated from the Medscape Portuguese edition using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.
A version of this article appeared on Medscape.com.