External validation of the modified CTP score based on ammonia to predict survival in patients with cirrhosis after TIPS placement

Abstract

This study aimed to perform the first external validation of the modified Child-Turcotte-Pugh score based on plasma ammonia (aCTP) and compare it with other risk scoring systems to predict survival in patients with cirrhosis after transjugular intrahepatic portosystemic shunt (TIPS) placement. We retrospectively reviewed 473 patients from three cohorts between January 2016 and June 2022 and compared the aCTP score with the Child-Turcotte-Pugh (CTP) score, albumin-bilirubin (ALBI), model for end-stage liver disease (MELD) and sodium MELD (MELD-Na) in predicting transplant-free survival by the concordance index (C-index), area under the receiver operating characteristic curve, calibration plot, and decision curve analysis (DCA) curve. The median follow-up time was 29 months, during which a total of 62 (20.74%) patients died or underwent liver transplantation. The survival curves for the three aCTP grades differed significantly. Patients with aCTP grade C had a shorter expected lifespan than patients with aCTP grades A and B (P < 0.0001). The aCTP score showed the best discriminative performance using the C-index compared with other scores at each time point during follow-up, it also showed better calibration in the calibration plot and the lowest Brier scores, and it also showed a higher net benefit than the other scores in the DCA curve. The aCTP score outperformed the other risk scores in predicting survival after TIPS placement in patients with cirrhosis and may be useful for risk stratification and survival prediction.

Keywords: Cirrhosis; Prediction model; Risk stratification; Survival; Transjugular intrahepatic portosystemic shunt.

Figure 1

Flowchart of the study.

Figure 2

Risk stratification of the aCTP score. (a) Kaplan–Meier curves show the transplant-free survival rate for the three grades of aCTP score: patients with an aCTP C grade had a lower transplant-free survival rate than patients with an aCTP A grade and B grade (P < 0.0001). (b) The distribution of the CTP and aCTP scores: 76 patients with CTP A were divided as follows: 59 with aCTP A and 17 with aCTP B; 177 patients with CTP B were divided into the following: 146 with aCTP B and 31 with aCTP C; and 46 patients with CTP C were still aCTP C. (c) Comparison of the transplant-free survival rates between aCTP A and aCTP B with CTP grade A: the mortality of aCTP B/CTP A was significantly higher than that of aCTP A/CTP A (p < 0.05). (d) Comparison of the transplant-free survival rate between aCTP B and aCTP C with CTP grade B: the mortality of aCTP C/CTP B was significantly higher than that of aCTP B/CTP B (p < 0.05).

Figure 3

The aCTP score performance in predicting post-TIPS mortality or LT. (a) C-index of the aCTP, CTP, ALBI, MELD, MELD-Na scoring systems at predicting post-TIPS mortality or LT during follow-up through 24 months: C-index of the aCTP score was greater than that of the other scores at predicting transplant-free survival at each time point of follow-up. (b) ROC curve of the aCTP, CTP, ALBI, MELD, and MELD-Na scoring systems for 2-year transplant-free survival: the AUROC of aCTP was greater than that of the other scores. (c) Calibration plot comparing the observed and predicted mortality or LT based on the aCTP, CTP, ALBI, MELD, and MELD-Na scoring systems in 2 years: The superior agreement between the observed and predicted mortality or LT by the aCTP score and ALBI score was revealed compared to the other scores. (d) DCA curve of the aCTP, CTP, ALBI, MELD, and MELD-Na scores in predicting 2-year transplant-free survival: the standardized net benefit of aCTP was higher than that of the other scores.