Use of the Mean Abnormal Result Rate (MARR) to Gauge Changes in Family Physicians' Selectivity of Laboratory Test Ordering, 2010-2015.

Objective: The mean abnormal result rate (MARR) has recently been advanced as a metric of laboratory test appropriateness. We used the MARR metric to examine patterns of change in family physician test requisitions over time.

Methods: We accessed the Laboratory Information System of Calgary Laboratory Services for family physician-ordered testing on outpatients to gather aggregate test and abnormal result counts from 2010 to 2015.

Results: Over the 6 years, there was an annual average of 3,401,553 tests for 411,295 distinct patients on their first test requisition for the year. The MARR increased from 8.1% to 9.0% through this period.

Conclusions: The MARR for Calgary and surrounding area gives tentative evidence of a gradual increase in physician test selectivity in recent years. Further data from other catchment areas are needed before making assertions about broader trends in physician awareness of laboratory resource use.