Nishteman Faysal MOHAMMAD, Amir Hani RAZIQ
Infectious Diseases and Clinical Microbiology - 2026;8(3):301-309
Objective: This study aimed to evaluate the diagnostic potential of serum microRNA-21 (miR-21) as a noninvasive biomarker for active pulmonary tuberculosis (PTB) and to compare its performance with conventional diagnostic methods, including smear microscopy and the GeneXpert MTB/RIF assay. Materials and Methods: A cross-sectional study was conducted between July 2024 and August 2025 in Duhok and Mosul, Iraq. Sputum samples were examined by Ziehl-Neelsen (ZN) staining, and selected samples were analyzed using the GeneXpert MTB/RIF assay. Serum samples were collected from patients with confirmed active PTB and healthy controls. Serum miR-21 expression levels were quantified using reverse transcription quantitative polymerase chain reaction (RT-qPCR), normalized to U6 small nuclear RNA as an internal reference, and analyzed using the comparative Ct (2-DeltaDeltaCt) method. Statistical analysis was performed using SPSS software, and a p-value of <= 0.05 was considered statistically significant. Results: A total of 474 sputum samples from patients suspected of PTB were examined. Serum miR-21 analysis was performed in 40 patients with confirmed PTB and 30 healthy controls. Serum miR-21 expression was significantly higher in patients with PTB compared with healthy controls (9.29 +/- 0.11 vs. 1.30 +/- 0.02; p = 0.0001), In other words, based on these two averages, it should be approximately 7.1-fold. However, if the authors arrived at 6.6 using a different DeltaDeltaCt calculation, they need to explain this. In addition, ZN smear microscopy detected acid-fast bacilli in 35 samples (7.4%). GeneXpert confirmed Mycobacterium tuberculosis in 31 of 150 samples (20.7%), including 10 smear-negative cases, and identified rifampicin resistance in 3 (9.7%) cases. Conclusion: Serum miR-21 was significantly upregulated in patients with active PTB, suggesting its potential as a noninvasive biomarker that may complement existing diagnostic methods. However, large-scale studies are needed to further validate its diagnostic value.
