ABSTRACT
Background: Nucleic acid amplification assays (NAAs), such as polymerase chain reaction or loop-mediated isothermal amplification (LAMP), are used for disease diagnosis. Current nucleic acid isolation kits require several hours for completion of protocol including the complicated handling steps. Objective: In this study, a simple and cost-effective nucleic acid preparation method was developed, and its performance was compared with those of commercial kits. Materials and Methods: RNA was prepared using our method and three commercial RNA isolation kits. The RNA quantity and quality were evaluated using the NanoDrop spectrophotometer and Agilent 2100 bioanalyser. Reverse transcription LAMP (RT-LAMP) reactions were performed to determine the usability of the RNA preparation methods. Results: The concentrations of RNA extracted from blood samples by four different methods were sufficient for use in NAAs. The RNA integrity number was >7.0 when RNA was isolated using other RNA isolation kits but lower when prepared using our method. The RT-LAMP reaction was successfully performed when RNA was prepared using any of the methods. Conclusions: These results demonstrate that despite the lower purity and integrity of RNA, our RNA preparation protocol is simple and rapid and shows reasonable performance in RT-LAMP.
ABSTRACT
Background: The microbiologic diagnosis of cutaneous tuberculosis is difficult because most lesions harbor only a small number of mycobacteria that cannot usually be detected by staining for the organism or by culture. Nucleic acid amplification tests based on the polymerase chain reaction (PCR) are potentially useful in this situation. Aims: To evaluate the utility of mRNA PCR and DNA PCR in the diagnosis of cutaneous tuberculosis. Methods: Biopsies from 28 cases of cutaneous tuberculosis and 19 controls with other diseases were subjected to microbiologic tests including direct smears for mycobacteria, culture and both mRNA PCR and DNA PCR. The laboratory was blinded to the clinical diagnosis. Results: None of the patients or controls showed a positive reaction on mRNA PCR test. Seven of 28 cases and 5 out of 19 controls showed a positive result on DNA PCR test yielding a sensitivity of 25% and a specificity of 73.7%. Conclusion: The results of PCR tests in cutaneous tuberculosis should be interpreted in the light of clinical and histopathological findings.