RESUMO
BACKGROUND: The Xpert MTB/RIF (Cepheid) non-laboratory-based molecular assay has potential to improve the diagnosis of tuberculosis (TB), especially in HIV-infected populations, through increased sensitivity, reduced turnaround time (2 h), and immediate identification of rifampicin (RIF) resistance. In a prospective clinical validation study we compared the performance of Xpert MTB/RIF, MTBDRplus (Hain Lifescience), LightCycler Mycobacterium Detection (LCTB) (Roche), with acid fast bacilli (AFB) smear microscopy and liquid culture on a single sputum specimen. METHODS AND FINDINGS: Consecutive adults with suspected TB attending a primary health care clinic in Johannesburg, South Africa, were prospectively enrolled and evaluated for TB according to the guidelines of the National TB Control Programme, including assessment for smear-negative TB by chest X-ray, clinical evaluation, and HIV testing. A single sputum sample underwent routine decontamination, AFB smear microscopy, liquid culture, and phenotypic drug susceptibility testing. Residual sample was batched for molecular testing. For the 311 participants, the HIV prevalence was 70% (nâ=â215), with 120 (38.5%) culture-positive TB cases. Compared to liquid culture, the sensitivities of all the test methodologies, determined with a limited and potentially underpowered sample size (nâ=â177), were 59% (47%-71%) for smear microscopy, 76% (64%-85%) for MTBDRplus, 76% (64%-85%) for LCTB, and 86% (76%-93%) for Xpert MTB/RIF, with specificities all >97%. Among HIV+ individuals, the sensitivity of the Xpert MTB/RIF test was 84% (69%-93%), while the other molecular tests had sensitivities reduced by 6%. TB detection among smear-negative, culture-positive samples was 28% (5/18) for MTBDRplus, 22% (4/18) for LCTB, and 61% (11/18) for Xpert MTB/RIF. A few (nâ=â5) RIF-resistant cases were detected using the phenotypic drug susceptibility testing methodology. Xpert MTB/RIF detected four of these five cases (fifth case not tested) and two additional phenotypically sensitive cases. CONCLUSIONS: The Xpert MTB/RIF test has superior performance for rapid diagnosis of Mycobacterium tuberculosis over existing AFB smear microscopy and other molecular methodologies in an HIV- and TB-endemic region. Its place in the clinical diagnostic algorithm in national health programs needs exploration. Please see later in the article for the Editors' Summary.
Assuntos
Infecções por HIV/complicações , Mycobacterium tuberculosis/isolamento & purificação , Técnicas de Amplificação de Ácido Nucleico/métodos , Tuberculose Resistente a Múltiplos Medicamentos/diagnóstico , Tuberculose Pulmonar/diagnóstico , Adulto , Idoso , Antibióticos Antituberculose/farmacologia , Proteínas de Bactérias/análise , Proteínas de Bactérias/genética , DNA Bacteriano/análise , DNA Bacteriano/genética , RNA Polimerases Dirigidas por DNA , Farmacorresistência Bacteriana/efeitos dos fármacos , Farmacorresistência Bacteriana Múltipla/efeitos dos fármacos , Feminino , HIV/patogenicidade , Infecções por HIV/epidemiologia , Humanos , Masculino , Pessoa de Meia-Idade , Mycobacterium tuberculosis/efeitos dos fármacos , Mycobacterium tuberculosis/genética , Reação em Cadeia da Polimerase , Estudos Prospectivos , Rifampina/farmacologia , Sensibilidade e Especificidade , África do Sul , Escarro/microbiologia , Tuberculose Resistente a Múltiplos Medicamentos/complicações , Tuberculose Resistente a Múltiplos Medicamentos/microbiologia , Tuberculose Pulmonar/complicações , Tuberculose Pulmonar/microbiologia , Adulto JovemRESUMO
The Abbott RealTime HIV-1 assay is a real-time nucleic acid amplification assay available for HIV-1 viral load quantitation. The assay has a platform for automated extraction of viral RNA from plasma or dried blood spot samples, and an amplification platform with real time fluorescent detection. Overall, this study found no clinically relevant differences in viral load, if samples were extracted manually.
