Abstract
In this study, we evaluated the diagnostic accuracy of multiple cross displacement amplification (MCDA) combined with real-time PCR platform in pulmonary tuberculosis (PTB) patients. Total 228 PTB patients and 141 non-TB cases were enrolled. Based on the analysis of the first available sample of all participants, MCDA assay showed a higher overall sensitivity (64.0%), with a difference of more than 10% compared with Xpert MTB/RIF (Xpert) assay (51.8%, P < 0.05) and combined liquid and solid culture (47.8%, P < 0.001) for PTB diagnosis. In particular, MCDA assay detected 31 probable TB patients, which notably increased the percentage of confirmed TB from 57.9% (132/228) to 71.5% (163/228). The specificities of microscopy, culture, Xpert and MCDA assay were 100% (141/141), 100% (141/141), 100% (141/141), and 98.6% (139/141), respectively. Among the patients with multiple samples, per patient sensitivity of MCDA assay was 60.5% (52/86) when only the first available sputum sample was taken into account, and the sensitivity increased to 75.6% (65/86) when all samples tested by MCDA assay were included into the analysis. Therefore, MCDA assay established in this study is rapid, accurate and affordable, which has the potential in assisting the accurate and rapid diagnosis of PTB and speed up initiation of TB treatment in settings equipped with real-time PCR platform.
Highlights
MATERIALS AND METHODSTuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is still a leading cause of mortality worldwide from a single infectious agent, being responsible for 9.9 million new cases and 1.3 million deaths in 2019 (World Health Organization [WHO], 2021)
multiple cross displacement amplification (MCDA) assay exhibited a sensitivity of 64.0% (146/228) in patients with active pulmonary tuberculosis (PTB), which was significantly higher than Xpert (51.8%, 118/228, P = 0.008), culture (MGIT and LJ combined, 47.8%, 109/228, P < 0.001) and microscopy (21.5%, 49/228, P < 0.001)
When all tested samples were considered individually, per sample sensitivity showed a sensitivity of 58.5% (110/188) for MCDA assay, which was significantly higher than Xpert (47.9%, P = 0.039), culture (44.1%, P = 0.005) and microscopy (26.1%, P < 0.001)
Summary
Tuberculosis (TB), caused by Mycobacterium tuberculosis (MTB), is still a leading cause of mortality worldwide from a single infectious agent, being responsible for 9.9 million new cases and 1.3 million deaths in 2019 (World Health Organization [WHO], 2021). Xpert is an automated real-time polymerase chain reaction (PCR) test with sensitivity comparable to liquid culture (Boehme et al, 2010) and is already widely used. Written informed consent was waived, as the specimens used in this study were leftover sputum samples from the clinical microbiology laboratory. (1) Bacteriologically confirmed TB: at least one positive result was obtained from the following tests: smear microscopy, culture or Xpert. Demographic information and clinical data of the enrolled subjects, including age, gender, treatment status, underlying diseases, were collected according to the medical records. The normalized fluorescence signal no less than 800 and reaction time no more than 35 min were used to determine MCDA positivity. Diagnostic accuracy parameters (sensitivity, specificity, positive and negative predictive values) were calculated using bacteriological results and clinical evidence as reference standards. SPSS version 23.0 software was used for statistical analysis
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