Use of laboratory tests in a teaching hospital: long-term trends: reductions in use and relative cost.

We have assessed long-term trends in the use of laboratory tests among patients hospitalized on the medical service of a large teaching hospital. A significant decline in numbers of chemistry tests and no growth in numbers of microbiology or hematology tests or roentgenograms were noted between 1970 and 1977. Per-patient increases in laboratory costs and charges were considerably less than increases in total hospitalization costs and charges. These findings contrast to an average increase of 13.8% per year in numbers of laboratory tests for hospital laboratories in this country between 1970 and 1975. Factors responsible for the observed stability in numbers of laboratory tests per patient per hospitalization included, but were not limited to, increased reliance on test batteries as opposed to individual tests; changing patterns of care leading to decreased use of nonautomated tests; and the impact of administrative and educational strategies directed toward optimum use of the laboratory.