Circulating Cell‐Free Mitochondrial DNA as a Prognostic Biomarker in Patients With HBV‐Related Acute‐on‐Chronic Liver Failure

ABSTRACT Acute‐on‐chronic liver failure (ACLF), particularly hepatitis B virus‐related ACLF (HBV‐ACLF), is a severe condition with high short‐term mortality. This study aimed to evaluate the prognostic value of circulating cell‐free mitochondrial DNA (cf‐mtDNA) in predicting short‐term mortality in HBV‐ACLF patients. A total of 320 HBV‐ACLF patients were included in the study population, with 192 patients in the derivation cohort and 128 in the validation cohort. Plasma cf‐mtDNA levels were quantified using qPCR. Plasma cf‐mtDNA levels were significantly elevated in HBV‐ACLF patients (3.95 log 10 copies/μL) compared to healthy controls (2.99 log 10 copies/μL) and patients with chronic liver disease (3.03 log 10 copies/μL) ( p < 0.001). Plasma cf‐mtDNA levels progressively increased with disease severity and were associated with multi‐organ failure. Sequential measurements of cf‐mtDNA showed a significant decrease in survivors (4.00 vs. 3.78 log 10 copies/μL, p = 0.019), while non‐survivors maintained persistently elevated levels with minimal change (4.19 vs. 4.15 log 10 copies/μL, p = 0.359). The cut‐off value of 3.9 log 10 copies/μL for cf‐mtDNA effectively stratified patients into high‐ and low‐risk groups, with significantly lower survival rates in the high‐risk group (28‐day: 46.2% vs. 86.0%, p < 0.001; 90‐day: 37.7% vs. 72.1%, p < 0.001). Using cf‐mtDNA in combination with key clinical parameters, we developed a novel prognostic score that exhibited superior predictive accuracy for 28‐ and 90‐day mortality (AUROCs: 0.907 and 0.906, respectively), outperforming established prognostic scores (all p < 0.05). These findings were validated in an independent cohort. Cf‐mtDNA is a superior biomarker for predicting short‐term mortality in HBV‐ACLF. Its association with multi‐organ failure and disease severity highlights the potential utility in early risk assessment and treatment optimization.