A, B, and C represent conditions. ~ is the NOT operator. n is the INTERSECTION operator and U is the UNION operator. SSI = surgical site infection.
This exhibit diagrams the compact logic that allows an algorithm to identify positive and negative instances of surgical site infection, based on the stepwise relationship between three conditions (A, B, and C). Preceding a condition with a tilde negates the presence of that condition (e.g., ~A means "not condition A"). Union and intersection operators from set theory are used to relate the sets of cases with or without each condition in a logic tree. This is explained in the text paragraphs before and after the Exhibit.