APACHE II is a well validated system for rating the severity of medical illness. It is an acronym that stands for "Acute Physiology And Chronic Health Evaluation". It is most frequently used to predict in-hospital death for patients in an intensive care unit. Previous scoring systems were based primarily on the patient's current medical state (for instance, rate of breathing or laboratory values). APACHE II incorporates pre-existing medical illnesses into its score (for example, diabetes), which is thought to make it more accurate.

The APACHE II system was first described in the journal Critical Care Medicine in 1985.

Reference

• Knaus WA, Draper EA, Wagner DP, Zimmerman JE. APACHE II: a severity of disease classification system. Crit Care Med 1985;13:818-29. Medline abstract (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=3928249) (PMID 3928249).