Objective: To study the clinical significance and reliability of strand displacement amplification (SDA) in detecting Mycobacterium tuberculosis complex.
Methods: SDA and fluorescence quantitative polymerase chain reaction (FQ-PCR) were employed to detect samples from 453 cases of tuberculosis, including 332 sputum samples, 78 samples of pleural effusion, and 43 samples of cerebrospinal fluid.
Results: In the 332 sputum samples, 131 were culture-positive, of which 110 samples (88 smear-positive) were Mycobacterium tuberculosis complex and 21 samples (20 smear-positive) were nontuberculous Mycobacteria. The sensitivity and specificity of SDA for the 110 samples of Mycobacterium tuberculosis complex and 21 samples of nontuberculous Mycobacteria were 99.1%, 95.2% and 94.6%, 95.2%, respectively. The positive rates in the 311 cases of Mycobacterium tuberculosis complex for SDA and FQ-PCR were 55.3% (172/311) and 47.0% (146/311), respectively. There were 20 smear positive samples in the 121 samples of pleural effusion and cerebrospinal fluid, of which 19 were Mycobacterium tuberculosis, 1 nontuberculous Mycobacterium. The positive rates for SDA and FQ-PCR were 43.4% (52/120) and 33.4% (40/120), respectively. Internal amplification control (IAC) was designed for SDA to achieve accuracy of the results.
Conclusion: The automatic assay system of SDA is a rapid and specific test for detecting Mycobacterium tuberculosis complex.