Different data systems, different conclusions? Comparing hospital use data for the aged from four data systems.

Four major national data systems collect data on short-stay hospital use by persons age 65 years and over. This paper examines the extent of agreement on the major statistics reported from the four systems and explains, as far as possible, the reasons for discrepancies among the data. The paper also offers some suggestions to the user of hospital care data. The study shows that for national trends the four systems agreed on number of admissions, average length of stay, and days of care. Comparisons across census regions revealed agreement on average length of stay, but showed an unanticipated lack of agreement on admissions. When we examined data on admissions and average length of stay by diagnosis and surgical procedure groups there was agreement among the data systems for most groups, but for certain groups wide differences occurred. The results emphasize the need for data users to understand the nature and limitations of the data they employ. The results also point to a need for data users to consult a number of sources whenever possible.