Detection and Quantification of Mycobacterium tuberculosis in the Sputum of Culture-Negative HIV-infected Pulmonary Tuberculosis Suspects: A Proof-of-Concept Study
Rationale Rapid diagnosis of pulmonary tuberculosis (TB) is critical for timely initiation of treatment and interruption of transmission. Yet, despite recent advances, many patients remain undiagnosed. Culture, usually considered the most sensitive diagnostic method, is sub-optimal for paucibacillary disease. Methods We evaluated the Totally Optimized PCR (TOP) TB assay, a new molecular test that we hypothesize is more sensitive than culture. After pre-clinical studies, we estimated TOP’s per-patient sensitivity and specificity in a convenience sample of 261 HIV-infected pulmonary TB suspects enrolled into a TB diagnostic study in Mbarara, Uganda against MGIT culture, Xpert MTB/RIF and a composite reference standard. We validated results with a confirmatory PCR used for sequencing M. tuberculosis. Measurements and Results Using culture as reference, TOP had 100% sensitivity but 35% specificity. Against a composite reference standard, the sensitivity of culture (27%) and Xpert MTB/RIF (27%) was lower than TOP (99%), with similar specificity (100%, 98% and 87%, respectively). In unadjusted analyses, culture-negative/TOP-positive patients were more likely to be older (P<0·001), female (P<0·001), have salivary sputum (P = 0·05), sputum smear-negative (P<0.001) and less advanced disease on chest radiograph (P = 0.05). M. tuberculosis genotypes identified in sputum by DNA sequencing exhibit differential growth in culture. Conclusions These findings suggest that the TOP TB assay is accurately detecting M. tuberculosis DNA in the sputum of culture-negative tuberculosis suspects. Our results require prospective validation with clinical outcomes. If the operating characteristics of the TOP assay are confirmed in future studies, it will be justified as a “TB rule out” test.
Section of Infectious Diseases, Department of Medicine, Boston Medical Center and Boston University School of Medicine, Boston, Massachusetts, United States of America;Thisis Diagnostics Inc., Boston, Massachusetts, United States of America;Epicentre, Médecins sans Frontières, Mbarara, Uganda;Mbarara University of Science and Technology, Mbarara, Uganda;Department of Biostatistics, Boston University School of Public Health, Boston, Massachusetts, United States of America;Núcleo de Doenças Infecciosas, Universidade Federal do Espírito Santo, Vitória, Brazil;Clinical Microbiology Laboratory, Boston Medical Center, Boston, Massachusetts, United States of America;Epicentre, Médecins sans Frontières, Mbarara, Uganda;Clinical Microbiology Laboratory, Boston Medical Center, Boston, Massachusetts, United States of America;Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America;Section of Infectious Diseases, Department of Medicine, Boston Medical Center and Boston University School of Medicine, Boston, Massachusetts, United States of America;Epicentre, Médecins sans Frontières, Mbarara, Uganda;Núcleo de Doenças Infecciosas, Universidade Federal do Espírito Santo, Vitória, Brazil;Public Health Research Institute (PHRI) – Rutgers University, Newark, New Jersey, United States of America;Thisis Diagnostics Inc., Boston, Massachusetts, United States of America;Núcleo de Doenças Infecciosas, Universidade Federal do Espírito Santo, Vitória, Brazil;Epicentre, Médecins sans Frontières, Mbarara, Uganda;Section of Infectious Diseases, Department of Medicine, Boston Medical Center and Boston University School of Medicine, Boston, Massachusetts, United States of America;Thisis Diagnostics Inc., Boston, Massachusetts, United States of America
Recommended Citation:
Guillermo Madico,Moses Mpeirwe,Laura White,et al. Detection and Quantification of Mycobacterium tuberculosis in the Sputum of Culture-Negative HIV-infected Pulmonary Tuberculosis Suspects: A Proof-of-Concept Study[J]. PLOS ONE,2016-01-01,11(7)