6 research outputs found
Colorimetric microwell plate reverse-hybridization assay for Mycobacterium tuberculosis detection
Colorimetric microwell plate reverse-hybridization assay for Mycobacterium tuberculosis detection
Direct smear examination using Ziehl-Neelsen staining for pulmonary
tuberculosis (PTB) diagnosis is inexpensive and easy to use, but has
the major limitation of low sensitivity. Rapid molecular methods are
becoming more widely available in centralized laboratories, but they
depend on timely reporting of results and strict quality assurance
obtainable only from costly commercial kits available in high burden
nations. This study describes a pre-commercial colorimetric method,
Detect-TB, for detecting Mycobacterium tuberculosis DNA in which an
oligonucleotide probe is fixed onto wells of microwell plates and
hybridized with biotinylated polymerase chain reaction amplification
products derived from clinical samples. The probe is capable of
hybridising with the IS6110 insertion element and was used to
specifically recognise the M. tuberculosis complex. When combined with
an improved silica-based DNA extraction method, the sensitivity of the
test was 50 colony-forming units of the M. tuberculosis reference
strain H37Rv. The results that were in agreement with reference
detection methods were observed in 95.2% (453/476) of samples included
in the analysis. Sensitivity and specificity for 301 induced sputum
samples and 175 spontaneous sputum samples were 85% and 98%, and 94%
and 100%, respectively. This colorimetric method showed similar
specificity to that described for commercially available kits and may
provide an important contribution for PTB diagnosis
Performance of a molecular assay to detect Mycobacterium tuberculosis complex DNA in clinical specimens: multicenter study in Brazil
BACKGROUND In high tuberculosis (TB) burden countries, there are few data on the performance of new molecular commercialised assays developed locally. OBJECTIVE To evaluate the performance of a new molecular commercialised assay for TB diagnosis (Detect-TB) in three laboratories. METHODS A total of 302 sputum samples from an equal number of patients with presumptive diagnosis of pulmonary tuberculosis (PTB) were submitted for routine smear microscopy, culture, and Detect-TB assay at three different sites in Brazil (the cities of Caxias do Sul, São Paulo and Canoas). FINDINGS Seventy four (24.7%) TB cases were diagnosed (65 bacteriologically confirmed). When compared to smear microscopy/culture results, the overall sensitivity and specificity of Detect-TB assay was 84.6% (CI 95%; 73.7-91.6) and 93.1% (CI 95%; 89.1-95.8), respectively. When compared to bacteriological and clinical diagnostic criteria, the sensitivity and specificity of Detect-TB assay was 74.3% (CI 95%; 63.3-82.9) and 92.9% (CI 95%; 88.7-95.6), respectively. Among the three sites - Caxias do Sul, São Paulo and Canoas - the sensitivity and specificity were respectively 94.7% and 97.8%; 71.4% and 93.9%, 82.1% and 88.9%. MAIN CONCLUSIONS These findings suggest that the Detect-TB assay could be applied routinely in reference laboratories across different regions in Brazil