PRISM is a physiology-based severity-of-illness score used in pediatric intensive care units (PICUs) to help quantify how sick a child is early in the ICU course and (in its original model) to estimate ICU mortality risk. It was developed to reduce the larger Physiologic Stability Index (PSI) into a smaller set of variables that were practical to collect in routine care. PubMed

What PRISM measures

The original PRISM score uses 14 clinical/laboratory parameters (e.g., blood pressure, heart rate, respiratory rate, oxygenation, blood gases, neurologic status, coagulation, and key chemistries). Each parameter contributes points only when abnormal, and the total score is the sum of points (higher = greater physiologic derangement). acta.tums.ac.ir

In typical use, PRISM is calculated using the most abnormal (worst) values over the early ICU time window (commonly the first 24 hours), so it reflects early physiologic instability rather than diagnosis alone. acta.tums.ac.ir+1

Mortality prediction (original PRISM model)

A commonly cited mortality model combines:

• the PRISM score,
• age (months), and
• operative status (postoperative vs nonoperative),

into a logistic equation to estimate probability of ICU mortality (and survival = 1 − mortality). acta.tums.ac.ir

Important note about versions

PRISM has been updated (e.g., PRISM III) with additional variables and refined modeling. PubMed
In practice, scoring systems like PRISM are often most reliable for groups/populations (benchmarking, quality comparison, risk adjustment) rather than as the sole basis for decisions about an individual patient.