The episode groupers utilize the primary diagnosis on claim line items to create and place the line items into episode. Only certain types of claims, as determined by procedure and revenue codes, can start an episode such as evaluation and management procedure codes, surgery procedure codes or specific inpatient facility revenue code. Conceptually, episodes are determined to be complete if one observes an adequate "clean period" ahead of the initial date on the claims and also observes an appropriate clean period after the final date on the claims. Clean periods, or intervals during which there are no claims associated with a given episode type, are used by the grouper packages to determine whether two claims are close enough together in time to be considered part of the same episode. Each episode type (ETG for Symmetry and MEG for Medstat) has an associated clean period that is set by the groupers on consultation with physicians. These clean periods range from 0 days to 999 days. Acute episode types have shorter clean periods; chronic episode types have longer clean periods. The notion of a clean period does not fit well with the concept of a chronic disease. With a three year window of data for our analysis, it is extremely difficult for chronic episodes to be deemed complete (since they need clean periods of 180 to 365 days.37) Recognizing this issue, episode groupers typically set fixed annual lengths for those episodes associated with chronic diseases, and one episode commonly immediately follows another; no clean periods are imposed. Following this convention, we rely on calendar years for measuring the lengths of chronic episodes.
Prior to running the episode groupers, the user must construct files to meet each grouper's specifications. Additionally, options in each grouper's configuration files must be set so the software properly reads the information on the input files and constructs episodes in a manner suiting the user's needs. MaCurdy et al. (2008) evaluated the functionality of each grouper in producing episodes of care using Medicare claims data and developed a set of baseline file configurations and settings adapted to structure of Medicare claims. The episodes for this analysis are created using the baseline settings established by MaCurdy et al., with one exception: Medstat episodes are created using an adaptation of the Build Admissions feature, which groups all claims concurrent with an inpatient stay to the episode associated with the stay. Following is a brief overview of the settings used to construct the episodes of care used in this analysis.