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Am J Clin Pathol. 2015 Nov;144(5):704-12. doi: 10.1309/AJCPYXDAUS2F8XJY.

Inappropriate repeats of six common tests in a Canadian city: a population cohort study within a laboratory informatics framework.

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From the Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada; Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, Toronto, Canada and.
Department of Pathology and Laboratory Medicine, University of Calgary and Calgary Laboratory Services, Calgary, Canada.



To identify inappropriate repeats of six common laboratory tests in a population sample of patients, using highly specific criteria based only on repeat time and test value.


We used a laboratory informatics database to conduct a retrospective cohort study using a population sample of 103,000 patients in the city of Calgary with an index test in 2010 and uniform follow-up of 1 year. We examined six tests (cholesterol, hemoglobin A1c, thyroid-stimulating hormone, vitamin B12, vitamin D, and ferritin) with consensus-based or easily justified criteria for inappropriate repeats based solely on time to repeat and the index test value.


The percentages of tests repeated at 3, 6, and 12 months were 11%, 23%, and 41%, respectively. In total, 16% of these six tests were inappropriately repeated, representing an annual internal cost of $0.6 to $2.2 million Canadian dollars and corresponding to population-scaled national estimates for Canada and the United States of $160 million and $2.4 billion, respectively.


Objective definitions based on repeated testing identified 16% of six studied tests as inappropriate, delineating a subset of inappropriate testing that is well suited to automated identification and intervention and that provides a likely lower bound on the true burden of inappropriate testing.


Cholesterol; Ferritin; HbA1c; Inappropriate testing; Laboratory utilization; Repeated testing; TSH; Vitamin B12; Vitamin D

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