Previous studies have identified methods of decreasing laboratory utilization. However, most were hospital-based, relatively small, single-centered, or of limited duration.
To determine the effect of 3 population-based interventions (physician guidelines, laboratory requisition form modification, and changes to funding policy) on laboratory utilization in Ontario.
Interventional time-series analysis in which data analysis was based on all claims made to the Ontario Health Insurance Program between July 1, 1991, and April 1997 for laboratory tests affected by the interventions.
All clinical laboratories (not based in hospitals) in Ontario.
Physician guidelines, modification of laboratory requisition form, and changes in funding policy for the use of the erythrocyte sedimentation rate test (ESR), microscopic urinalysis, tests for renal function, iron stores, serum urea, and serum iron determinations, and tests for thyroid dysfunction (total thyroxine and thyroid-stimulating hormone [TSH]).
Change from 1991 to 1997 in utilization rates of ESR, microscopic urinalysis, serum urea and iron determinations, and tests for total thyroxine and TSH.
Age- and sex-standardized rates for laboratory tests unaffected by the interventions were stable during the study period. Utilization of ESR and urea determination decreased by 58% (P