Reducing the number of T3 orders in the Paris hospital network: towards better appropriatness of thyroid function test prescription.

In vitro thyroid function tests are among the most frequently prescribed laboratory procedures. Serum triiodothyronine (T3) tests are seldom necessary as a first-level measurement. Our objectives were to measure the proportion of T3 measurements relative to all in vitro thyroid function tests in a large hospital network and to investigate the contributions of various interventions to change prescribers'behavior. We performed two cross-sectional surveys in 1995 and 1998 in the 50 Paris University hospitals. Questionnaires were mailed to the heads of the 30 laboratories performing thyroid function tests. One-month orders of free and total thyroxine, free and total T3 and thyrotropin were recorded; changes in T3 measurement orders between the two periods were estimated and association with interventions were expressed as odds ratios and 95% confidence intervals. Twenty-five heads of laboratory responded to both surveys. In 1995, T3 measurements constituted 21% of in vitro thyroid function test ordering, which seems to us exceedingly high. The decrease in T3 measurement ordering observed in 1998 (15% of thyroid function test ordering) was independently associated with multiple behavioral changes: educational interventions, structured test form use and year of prescription.