A modified Child-Turcotte-Pugh score based on plasma ammonia predicts survival for patients with decompensated cirrhosis

BACKGROUND: Plasma ammonia has been shown to be an independent prognostic factor for patients with liver cirrhosis. AIM: We aimed to investigate the discrimination and calibration of a new prognostic model (aCTP) based on plasma ammonia (Amm) replacing hepatic encephalopathy (HE) in the Child-Turcotte-Pugh (CTP) score. DESIGN: Diagnostic test, paired design. METHODS: Baseline Amm levels were corrected to the upper limit of normal (Amm-ULN). We designed the new model based on the cut-off value of Amm-ULN in the observational cohort of 554 clinically stable cirrhotic patients from January 2012 to July 2019. External validation was carried out using prospective data from 185 patients with liver cirrhosis. RESULTS: Our analysis showed that each 1-point increase in Amm-ULN was associated with a 2-fold increase in the likelihood of mortality [hazard ratio (HR), 2.06; 95% CI: 1.81–2.36, P < 0.001]. In the aCTP score, Amm-ULN < 1.0 was defined as a score of 1, 1.0 ≤ Amm-ULN < 1.4 as 2 and ≥1.4 as 3. The survival curves among three aCTP grades were significantly different (P < 0.0001). The aCTP score showed the better agreements between predicted and observed events in the validating cohorts than the CTP score (C-statistics: 0.75 and 0.69, P < 0.001). The aCTP score showed inspiring power to predict acute decompensation (C-statistics: 0.76; 95% CI: 0.71–0.81) and acute-on-chronic liver failure (C-statistics: 0.81; 95% CI: 0.77–0.86). CONCLUSION: This study demonstrates the feasibility and the potential for plasma Amm replacing HE (aCTP) to enhance the prognostication of transplant-free survival provided by the CTP score for patients with decompensated cirrhosis.