We investigated microRNAs (miRNAs) as potential prognostic biomarkers for equine sarcoid (ES) disease. In a breed-, age-, and sex-matched case-controlled study involving 45 ES-affected and 15 control horses, we assessed the diagnostic, prognostic, and theragnostic value of 3 miRNAs (eca-miR-127, eca-miR-379, eca-miR-432) in horses treated with European mistletoe (Viscum album) extract versus placebo. Whole-blood miRNA concentrations were measured using reverse-transcription quantitative real-time PCR (RT-qPCR) at 3 different times. We found that eca-miR-432 expression was lower in ES-affected (median = −1.93; 95% CI: −2.03 to −.86) compared to control (median = −1.71; 95% CI: −1.92 to −1.6) horses (p = 0.03, r = 0.3; 95% CI: 0.024–0.57) with a median difference of −1.93 versus −1.71, respectively. The ROC curve analysis indicated an area under the curve of 0.71 (95% CI: 0.51–0.84; p = 0.005) with a sensitivity of 74% (95% CI: 61–88%) and a specificity of 73% (95% CI: 39–94%) to diagnose ES. However, none of the miRNAs evaluated had prognostic potential or significant changes in expression following treatment. Additionally, miRNA expression was not influenced by breed, sex, or season. Although whole-blood eca-miR-432 had moderate diagnostic potential for ES, identifying prognostic miRNA biomarkers for ES remains a challenge.
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