Introduction:
Previous studies have found that RAP may be at reduced risk for a clinically severe course and have reduced mortality. However, there is still a lack of data related to RAP admitted to ICU.

Material and methods:
Baseline characteristics of patients diagnosed with IAP and RAP from the MIMIC-IV database were extracted. In-hospital mortality and length of hospital/ICU stay were identified as outcomes. Binomial logistic regression analysis was performed to clarify the independent risk factors for in-hospital mortality in both groups, and we determined the best scoring system for prognosis prediction by plotting the ROC curves and DCA curves.

Results:
The in-hospital mortality rate was 13.96% in patients with IAP and 3.57% in patients with RAP. For IAP, the CCI, the BISAP score, and the SIRS score on the first day of admission were independent risk factors for in-hospital mortality. The SAPS II score almost always showed a higher net clinical benefit than the other scoring systems (BISAP, LODS, and OASIS). The BISAP score almost always showed a higher net clinical benefit than the others for RAP.

Conclusions:
RAP is less severe and has a lower risk of in-hospital mortality than IAP. The CCI, the BISAP score, and the SIRS score on the first day of admission were all independent risk factors for in-hospital mortality in patients with IAP. The SAPS II score was a better scoring system for predicting in-hospital mortality in patients with IAP. The BISAP score showed potential for predicting in-hospital mortality in patients with RAP.