Performance of diagnostic tests for pulmonary tuberculosis in indigenous populations in Brazil: the contribution of Rapid Molecular Testing

Abstract

Objective: To evaluate the accuracy of rapid molecular testing as a diagnostic tool and estimate the incidence of smear-positive pulmonary tuberculosis among the indigenous population. Methods: This is an epidemiological study based on secondary data. We calculated the incidence of smear-positive pulmonary tuberculosis between January 1st, 2011 and December 31, 2016, and the performance of bacilloscopy and rapid molecular testing in diagnosing pulmonary tuberculosis compared to sputum culture (standard test). Results: We included 4,048 cases of indigenous people with respiratory symptoms who provided sputum samples for analysis. Among them, 3.7%, 6.7%, and 3.7% had positive results for bacilloscopy, sputum culture, and rapid molecular testing, respectively. The mean incidence of pulmonary tuberculosis was 269.3/100 thousand inhabitants. Rapid molecular testing had 93.1% sensitivity and 98.2% specificity, compared to sputum culture. Bacilloscopy showed 55.1% sensitivity and 99.6% specificity. Conclusions: Rapid molecular testing can be useful in remote areas with limited resources and a high incidence of tuberculosis, such as indigenous villages in rural regions of Brazil. In addition, the main advantages of rapid molecular testing are its easy handling, fast results, and the possibility of detecting rifampicin resistance. Together, these attributes enable the early start of treatment, contributing to reduce the transmission in communities recognized as vulnerable to infection and disease.

Identification of a predominant genotype of Mycobacterium tuberculosis in Brazilian indigenous population

“…Ziehl–Neelsen bacilloscopy was performed until 2014 when GeneXpert took its place. Ministry of Health’s TB protocol 57 , positive bacilloscopy/GeneXpert results should be confirmed by the culture at the General Laboratory of MS; this confirmation is not always possible due to logistical challenges in getting samples to the laboratory 58 on top of well-documented difficulties with successfully culturing M. tuberculosis 59 .…”

Effectiveness and trend forecasting of tuberculosis diagnosis after the introduction of GeneXpert in a city in south-eastern Brazil

“…Across the world, the most commonly used tests for the diagnosis of TB are the sputum smear and sputum culture tests (only for pulmonary TB, in cases of extrapulmonary TB, diagnostic tests are performed with other materials). As it is simpler, faster and less costly, smear microscopy ends up being more commonly used as a routine test by health systems, but it is worth mentioning that it has low sensitivity, especially in cases with low bacillary load [ 33 , 34 ].…”

“…The sensitivity of the culture varied between 70% and 90% when the sample of the material was correctly collected, stored and all procedures for carrying out the test were correctly followed by the responsible professional, using a work-intensive method that requires qualified professionals for the examination to be carried out accurately and reliably. It takes about 14 to 60 days to get a result with this technique and due to the long period required to reach a diagnosis, culture is rarely used to make decisions regarding the treatment of a person with TB [ 33 , 34 ]. It is worth mentioning that the most used culture media are solids, but liquid culture performed in an automated system has advantages.…”

Tuberculosis series 2019

“…In our tuberculosis series, the diagnosis of tuberculosis is addressed in four original articles. (5)(6)(7)(8) Since its introduction in 2010, the molecular test for Mycobacterium tuberculosis and its resistance to rifampin (Xpert MTB/RIF assay) is increasingly used as the initial diagnostic test for tuberculosis in many countries. (9,10) Two of the articles in our series addressed the use of the Xpert MTB/RIF assay.…”

“…(9,10) Two of the articles in our series addressed the use of the Xpert MTB/RIF assay. (5,6) In the first, (5) a retrospective study conducted at a tertiary referral center, the authors showed that the Xpert MTB/RIF assay is a highly accurate method of detecting tuberculosis and rifampin resistance in sputum, BAL fluid, and tracheal aspirate samples. In the second article, (6) the sensitivity and specificity of the Xpert MTB/RIF assay were evaluated in a population of indigenous Brazilians.…”