Integrated Plasma miR-15a-5p, Inflammatory Markers, and PBMC Cell-Cycle Genes for Distinguishing Active from Latent Tuberculosis: A Cross-Sectional Diagnostic Study

<title>Abstract</title> <p> Background Distinguishing active tuberculosis (ATB) from latent tuberculosis infection (LTBI) remains challenging. This study evaluated plasma miR-15a-5p, inflammatory markers, and peripheral blood mononuclear cell (PBMC) cell-cycle-related genes as candidate biomarkers for tuberculosis classification. Methods In this single-centre cross-sectional diagnostic study, 50 patients with ATB, 50 individuals with LTBI, and 50 healthy controls were enrolled. Plasma and PBMC expression of miR-15a-5p, <italic>CCND1</italic> , <italic>CCND2</italic> , and <italic>CDK6</italic> was measured using RT-qPCR, while plasma C-reactive protein (CRP) and interleukin-6 (IL-6) were measured using routine clinical platforms. Diagnostic performance was assessed using receiver operating characteristic analysis. A multivariable logistic regression model combining plasma miR-15a-5p, CRP, and IL-6 was internally validated using 1,000 bootstrap resamples. Public miRNA and transcriptomic datasets were analysed to assess reproducibility, compartment specificity, and treatment-associated changes. Results Plasma miR-15a-5p, CRP, and IL-6 were significantly elevated in ATB. Plasma miR-15a-5p distinguished ATB from healthy controls with an area under the curve (AUC) of 0.846. In PBMCs, <italic>CCND1</italic> was downregulated and <italic>CCND2</italic> was upregulated in both LTBI and ATB, whereas <italic>CDK6</italic> showed no significant difference. For distinguishing ATB from LTBI, miR-15a-5p, CRP, and IL-6 individually yielded AUCs of 0.740, 0.756, and 0.793, respectively. Their combination achieved an AUC of 0.920, with a bootstrap-corrected AUC of 0.913, 90% sensitivity, 86% specificity, and 88% accuracy. Public datasets revealed compartment- and cell-subset-specific expression patterns, including a treatment-associated increase in classical-monocyte <italic>CCND2</italic> . Conclusions Plasma miR-15a-5p combined with CRP and IL-6 improved the discrimination of ATB from LTBI, while PBMC <italic>CCND1</italic> and <italic>CCND2</italic> reflected tuberculosis-associated transcriptional changes. External multicentre validation is required before clinical application. </p>