BackgroundElevated international normalized ratio of prothrombin time (PT-INR) is one of the key characteristics of acute-on-chronic liver failure (ACLF). Whether the staging of PT-INR has the ability to screen out subgroups of ACLF patients who would be more eligible for artificial liver support system (ALSS) treatment has not been studied in detail.MethodsA previous study enrolled patients receiving ALSS treatment with regional citrate anticoagulation from January 2018 to December 2019. Patients with different PT-INR intervals were retrospectively enrolled: 1.3 ≤ PT-INR < 1.5 (Pre-stage), 1.5 ≤ PT-INR < 2.0 (Early-stage), 2.0 ≤ PT-INR < 2.5 (Mid-stage), and PT-INR ≥ 2.5 (End-stage). The Cox proportional hazards models were used to estimate the association between stages of ACLF or sessions of ALSS treatment and 90 day mortality.ResultsA total of 301 ACLF patients were enrolled. The 90 day mortality risk of Early-stage ACLF patients (adjusted hazard ratio (aHR) (95% confidence interval (CI)), 3.20 (1.15–8.89), p = 0.026), Mid-stage ACLF patients (3.68 (1.34–10.12), p = 0.011), and End-stage ACLF patients (12.74 (4.52–35.91), p < 0.001) were higher than that of Pre-stage ACLF patients, respectively. The 90 day mortality risk of Mid-stage ACLF patients was similar to that of Early-stage ACLF patients (1.15 (0.69–1.94), p = 0.591). The sessions of ALSS treatment was an independent protective factor (aHR (95% CI), 0.81 (0.73–0.90), p < 0.001). The 90 day mortality risk in ACLF patients received 3–5 sessions of ALSS treatment was lower than that of patients received 1–2 sessions (aHR (95% CI), 0.34 (0.20–0.60), p < 0.001), whereas the risk in patients received ≥6 sessions of ALSS treatment was similar to that of patients received 3–5 sessions (0.69 (0.43–1.11), p = 0.128).ConclusionACLF patients in Pre-, Early-, and Mid-stages might be more eligible for ALSS treatment. Application of 3–5 sessions of ALSS treatment might be reasonable.