External Validation of the FIPS Score for Post-TIPS Mortality in a National Veterans Affairs Cohort

Background The Freiburg index of post-TIPS survival (FIPS) score was recently demonstrated to improve prediction of post-TIPS mortality relative to existing standards. As this score was derived from a German cohort over an extended time period, it is unclear if performance will translate well to other settings. This study aimed to externally validate the FIPS score in a large Veterans Affairs (VA) cohort over two separate eras of TIPS-related care. Methods This was a retrospective cohort study of patients with cirrhosis who underwent TIPS placement in the VA from 2008 to 2020. Cox regression models for post-TIPS survival were constructed using FIPS, MELD, MELD-Na, or CTP scores as predictors. Discrimination (Harrell's C) and calibration (joint tests of calibration curve slope and intercept) were evaluated for each score. A stratified analysis was performed for time periods between 2008-2013 and 2014-2020. Results The cohort of 1,274 patients was 97.3% male with mean age 60.9 years and mean MELD-Na 14. The FIPS score demonstrated the highest overall discrimination versus MELD, MELD-Na, and CTP (0.634 vs. 0.585, 0.626, 0.612, respectively). However, in the modern treatment era (2014-2020), the FIPS score performed similarly to MELD-Na. Additionally, the FIPS score demonstrated poor calibration at one-month and six-month post-TIPS timepoints (joint p = 0.04 and 0.004, respectively). MELD, MELD-Na, and CTP were well-calibrated at each timepoint (each joint p > 0.05). Conclusion The FIPS score performed similarly to MELD-Na in the modern TIPS treatment era and demonstrated regions of poor calibration. Future models derived with contemporary data may improve prediction of post-TIPS mortality.