The 2003 Index of Hospital Quality

Phase I
have their own hierarchical method for determining severity of illness and will be
discussed later. The four severity of illness subclasses are:
Subclass (PSC) Severity of Illness
1 Minor (Includes non CC)
2 Moderate
3 Major
4 Extreme
The severity of illness subclass is used in conjunction with the patient’s base APR-
DRG for analysis such as evaluating resource intensity or patient care outcomes.
A patient’s severity of illness subclass should not be used with their DRG because
several DRGs may form one APR-DRG. Therefore, since severity of illness
subclasses correspond to the APR-DRG number and not the DRG, it is important
to use the APR-DRG number to accurately interpret data.
The process for assigning a patient a severity of illness subclass is a three phase
process and is summarized as follows:
C Secondary diagnoses that are closely related to the principal diagnosis are
eliminated from further analysis.
C Remaining secondary diagnoses are assigned one of four distinct Standard Severity
of Illness Levels. Figure 1 presents examples of secondary diagnoses in each
severity of illness level.