Care fragmentation, quality, and costs among chronically ill patients.

To assess the relationship between care fragmentation and both quality and costs of care for commercially insured, chronically ill patients.We used claims data from 2004 to 2008 for 506,376 chronically ill, privately insured enrollees of a large commercial insurance company to construct measures of fragmentation. We included patients in the sample if they had chronic conditions in any of the following categories: cardiovascular disease,...