WHAT IS THE ISSUE?: Lab test overuse can contribute to further unnecessary follow-up and testing, negative patient experiences, potentially inappropriate treatments, and the inefficient use of health care resources. One review of lab testing in Canada found that around 22% of blood tests were likely unnecessary. One strategy to address lab test overuse is to establish minimal retesting intervals that can be implemented in medical laboratories to help identify and manage potentially inappropriate lab test requests. Minimum retesting intervals suggest the minimum time before a test should be repeated based on the biochemical properties of the test and the clinical situation in which it is used. They are intended to inform clinical decisions about repeat testing. The importance of lab resource stewardship is being addressed by Choosing Wisely Canada through Using Labs Wisely, a consortium of more than 150 hospitals committed to driving the appropriate use of lab testing in Canada. The hospitals participating in Using Labs Wisely identified a need for guidance on minimum retesting intervals for commonly used lab tests.

WHAT DID WE DO?: Choosing Wisely Canada and CADTH partnered to convene an independent time-limited advisory panel to develop consensus-based recommendations for minimum retesting intervals for 7 commonly used lab tests (antinuclear antibody [ANA], B-type natriuretic peptide [BNP] and N-terminal pro b-type natriuretic peptide [NT-proBNP], Hemoglobin A1C, lipase, lipid panel, serum protein electrophoresis [SPEP], and thyroid stimulating hormone [TSH]) in prespecified patient populations. The advisory panel included core and specialist members who were recruited from across Canada. The 7 core advisory panel members brought together expertise in laboratory medicine, family practice, and patient lived experience. Seven additional specialist members brought expertise in endocrinology, cardiology, pediatric cardiology, rheumatology, hematology oncology, gastroenterology, and general internal medicine. The Advisory Panel on Minimum Retesting Intervals considered patient group input, evidence from focused literature reviews, equity considerations, and clinical expertise. Through facilitated discussion, they reached consensus on the recommendations for minimum retesting intervals. Following external feedback, the recommendations for BNP and NT-proBNP and lipid panels were removed, and this document includes recommendations for minimum retesting intervals for 5 lab tests. These are not recommendations for repeat testing. They are recommendations that if testing is undertaken, it should not be repeated sooner than the indicated intervals. They are not intended to replace clinical judgment as there may be exceptions in which the recommendations do not apply.

WHAT IS THE POTENTIAL IMPACT?: The recommendations on minimum retesting intervals can support the hospitals participating in Choosing Wisely Canada’s Using Labs Wisely program in their effort to reduce unnecessary lab tests and their impact on patients, providers, health systems, and the environment. The recommendations may also be relevant to community and hospital lab stewardship efforts and may address the appropriate use of the 5 lab tests by enabling changes in lab test ordering in both inpatient and outpatient settings.