Rates of inappropriate laboratory test utilization in Ontario

Medical laboratory tests ordered redundantly represent one of the targets for reducing diagnostic testing without negatively, and possibly positively, affecting patient care. We study a clearly defined category of excessive laboratory utilization for nine analytes where inappropriate diagnostic testing is defined in terms of the time interval between tests; that is, ordering a test too soon following the previous order of the same test.

Population data from the near universal public Ontario Health Insurance Plan for the years 2006-2010 are employed where the tests are fulfilled by community medical laboratories. The analytes selected for consideration are thyroid stimulating hormone, hemoglobin A1c, lipid profile, serum protein electrophoresis, immunofixation, quantitative immunoglobulins, Vitamin D, Vitamin B12, and folate.

For the nine analytes studied, the percentage of inappropriate tests ranged from 6% to 20%. Large proportions of these inappropriate tests were completed >2weeks prior to the minimum threshold to reorder defined by practice guidelines and/or were repeated excessively within a year. Between 60% and 85% of the time, the ordering physician of an inappropriate test was the same physician who ordered the previous test. Specialists were more likely than primary care physicians to order repeat tests too soon.

A sizeable proportion of testing for these analytes was inappropriate according to practice guidelines. It is recommended that systems for preventing unnecessary repeat testing are investigated by the funding agencies and that reducing inappropriate testing be considered as a design element for electronic medical records and related information technology systems.