Abstract
ABSTRACT INTRODUCTION: Pulmonary tuberculosis caused by Mycobacterium tuberculosis is a serious public health problem affecting millions of people worldwide. The development of easy and low-cost diagnostic methods is crucial for disease control in rural remote and poverty areas and among vulnerable groups. OBJECTIVE: To evaluate the accuracy of laboratory methods for the diagnosis of Pulmonary tuberculosis. MATERIAL AND METHODS: Sputum samples from patients with clinical signs and symptoms were analyzed by microscopy after chemical treatment and spontaneous sedimentation and compared with methods employed routinely: direct sputum smear microscopy, culture, and GeneXpert®MTB/RIF. RESULTS: From the samples analyzed, 16% were positive by microscopy in the processed samples, 18% by both culture and Xpert®MTB/RIF, while 13% in the direct microscopy. The processed samples showed a 31% increase in positivity (57 samples) compared to conventional direct microscopy. In the analysis of the accuracy of the evaluated methods, all the results were statistically significant proving that they were not randomly positive or negative and confirming that there is a tendency for these results. CONCLUSION: Chemical treatment and spontaneous sedimentation of the sputum samples procedure represent an effective diagnostic tool in situations where more advanced technologies are not feasible. Besides the higher accuracy and greater detection of positive cases regarding the direct smear, the procedure strengthens biosafety by decreasing the risks of aerial contamination by Mycobacterium tuberculosis for laboratory professionals.
Highlights
Pulmonary tuberculosis caused by Mycobacterium tuberculosis is a serious public health problem affecting millions of people worldwide
This study evaluated the accuracy of a modified direct sputum smear microscopy (DSSM), with previous chemical treatment of the sputum samples with bleach [sodium hypochlorite (NaClO)] and spontaneous sedimentation, compared to routine methods used by public health laboratory services for Pulmonary tuberculosis (PTB) diagnosis
An aliquot of each sample was immediately used for conventional direct sputum smear microscopy, for culture inoculation, and for molecular analyses by the Xpert® MTB/RIF (Cepheid Inc Sunnyvale, CA, USA) system and the remaining portion of sputum was used for the modified DSSM method, with chemical treatment with commercial bleach, as described below
Summary
Pulmonary tuberculosis caused by Mycobacterium tuberculosis is a serious public health problem affecting millions of people worldwide. Besides the higher accuracy and greater detection of positive cases regarding the direct smear, the procedure strengthens biosafety by decreasing the risks of aerial contamination by Mycobacterium tuberculosis for laboratory professionals. Pulmonary tuberculosis (PTB) caused by Mycobacterium tuberculosis (Mtb) has been affecting humans for millennia and still affects millions of people annually and is considered one of the top 10 causes of death worldwide[1, 2]. The disease can be diagnosed by clinical history, chest X-ray, chest computed tomography (CT), bronchoscopy, tuberculin skin test or Mantoux reaction, the conclusive diagnosis requires the isolation and identification of the Mtb by laboratory tests such as direct smear microscopy, culture, and molecular biology techniques[1, 2]. According to the laboratory standards, its detection threshold can reach 10 bacilli/ml of sputum, but it has the disadvantage of being a complex, laborious and timeconsuming methodology, taking up to 8-12 weeks, before a negative Mtb growth result is reported, and requiring complex laboratory facilities and containment level 3 (BSL3) conditions[2, 3]
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