ABSTRACT
Background and Objectives: The role of microRNAs (miRNAs) in tuberculosis infection is well established. As microRNAs are able to change expression profiles according to different conditions, they can be useful biomarkers. Iranians and Afghans with tuberculosis were studied for three immune-related miRNAs (miR-let-7f, miR-125a, and miR-125b). Materials and Methods: A total of 60 Iranian and Afghan patients with active pulmonary TB were enrolled in the Pulmonary Department of the Pasteur Institute of Iran. Serum and sputum samples were collected simultaneously from all participants. A Real-time PCR was conducted to detect differentially expressed miRNAs. Results: Iranian (P<0.0001) and Afghan (P<0.0001) serum samples and Afghan (P<0.0001) sputum samples overexpressed miR-125a, whereas Iranian sputum samples showed downregulation (P=0.0039). In both Iranian (P<0.0001; P=0.0007) and Afghan (P<0.0001; P<0.0001) serum and sputum samples, miR-125b was overexpressed. Furthermore, miR-let-7f down-regulation was observed in serum and sputum samples (P<0.0001), whereas Iranian sputum samples had no statistically significant differences (P=0.348). Conclusion: Overexpression of miR-125a and miR-125b has been detected in Iranian and Afghan samples. In both races, miR-let-7f downregulation has been confirmed. Identification of miRNA profiles under different conditions opens the door to evaluating potential new biomarkers for diagnosis, disease monitoring, and therapeutic markers in TB infection.
ABSTRACT
Mycobacterium tuberculosis, acid fast bacilli from the family of Mycobacteriaceae, is the causative agent of most cases of tuberculosis. Tuberculosis, as a communicable disease, remains a serious public health threat, killing more than one million people globally every year. Primary diagnosis of tuberculosis bacilli (TB) relies mainly on microscopic detection of acid fast bacilli (AFB), but the method suffers from low sensitivity and the results largely depend on the technician's skill. New diagnostic tools are necessary to be introduced for rapid and accurate detection of the bacilli in sputum samples. We, in collaboration with Anda Biologicals, have developed a new platform, named as "Patho-tb", for rapid detection of AFB with high sensitivity and with low dependence on human skills. Evaluation of Patho-tb test performance was done in two settings: (1) primary field study conducted using 38 sputa from high TB prevalence area of Iran (Zabol city near to the Afghanistan border), and (2) main study conducted using 476 sputa from Tehran, capital of Iran. Patho-tb was applied for processed sputum samples in parallel with routine diagnostic methods (including AFB microscopy, culture and PCR). All test results were compared to final clinical diagnostic state of an individual and diagnostic sensitivity (DSe), specificity, positive predictive value, negative predictive value and accuracy of each test results were calculated using standard formulations. Analytical sensitivity and specificity of the Patho-tb test were also determined. Calculated values for five above mentioned parameters are as follows: for field study: AFB (DSe: 29.6, DSp: 81.8, PPV: 80, NPV: 23.1, AC: 44.7), Patho-tb (DSe: 63, DSp: 72.7, PPV: 85, NPV: 44.4, AC: 65.8), and for main study: AFB (DSe: 86.1, DSp: 99.4, PPV: 98.5, NPV: 93.9, AC: 95.2), Patho-tb (DSe: 97.4, DSp: 92.9, PPV: 86.5, NPV: 98.7, AC: 94.3). Reproducibility of Patho-tb test results were near to 100% (Cohen's kappa value between 0.85 and 1). The detection limit of Patho-tb test with 100% positivity rate was 3 × 103 cells/ml of sputum. In the field study, Patho-tb test was 33.4% more sensitive than AFB microscopy, while the improvement was only 11.3% during the main study. Patho-tb results are easy to interpret and the test can be merged with other screening tests, like AFB. Totally, Patho-tb test alone or in conjunction with AFB microscopy is a useful screening tool for TB detection especially in poor geographical lab conditions.
