Population-based study of repeat laboratory testing.

BACKGROUND Test repetition could be a readily modifiable component of laboratory utilization. Laboratory test repetition has not been rigorously studied at a population-based level. Our objective was to determine the prevalence of, and charges associated with, repetition of eight common laboratory tests. METHODS We performed a cross-sectional study using high-quality, population-based clinical databases that included adults in Eastern Ontario, Canada, between September 1999 and September 2000 for incidence of repeating eight common laboratory tests (hemoglobin, sodium, creatinine, thyrotropin, total cholesterol, HDL-cholesterol, ferritin, and hemoglobin A(1C)). Tests were classified as potentially redundant if repeated within the test's baseline testing interval. For creatinine, sodium, and hemoglobin, only tests repeated in the community were considered. For a sensitivity analysis, we varied the repeat interval by 25%, excluded tests repeated by different physicians, and excluded repeats of normal tests. RESULTS Almost 4 million tests were conducted during the study year. Most tests (76%) were conducted on patients in the community. More than one-half of all people in the population had at least one laboratory test, with an overall testing rate of 367 tests per 100 people per year. Repeat testing within 1 month accounted for 30% of all utilization (109 repeat tests per 100 people per year). Repetition was more common in hospitalized patients, varied extensively among tests, and was concentrated in a limited number of people. For the eight tests included in the study, charges of potentially redundant repetition in adults totaled between 13.9 and 35.9 million dollars (Canadian) annually. CONCLUSIONS Laboratory test repetition is very common, makes up a significant component of overall test utilization, and is costly.