Multicenter Benchmark Study Reveals Significant Variation in Thyroid Testing in the United States

Background: Studies show that a significant portion of laboratory testing is unnecessary. Thyroid tests are some of the most commonly ordered laboratory tests. Yet, little is known about practice patterns for laboratory testing for thyroid disease. The objective of this study was to collect data on practice patterns for thyroid testing in the United States. Methods: A survey was conducted to collect data on annual test volumes for thyrotropin (TSH), free thyroxine (fT4), total thyroxine (TT4), free triiodothyronine (fT3), total triiodothyronine (TT3), triiodothyronine uptake (T3U), reverse triiodothyronine (rT3), and complete blood counts (CBC). Sites were also asked to provide data on laboratory utilization management activities. Thyroid workup rates were compared using the TSH/CBC ratio. Thyroid test selection patterns were compared using the ratio of order volumes for thyroid tests relative to TSH. Results: Data were obtained from 82 sites. The thyroid workup rate (TSH/CBC) was higher for outpatients (0.26) than for inpatients (0.03). Based on median values, sites ordered 14 fT4, three TT4, four fT3, two TT3, 0.1 rT3, and 0.1 T3U for every 100 TSH orders. The majority (approximately 90%) of orders for T4 were for fT4 rather than TT4. Orders for T3 were almost evenly split between fT3 and TT3. There was significant practice variation in test selection for all tests. The highest variability was for the rT3/TSH and T3U/TSH ratios. Most organizations reported at least some laboratory utilization management activities. There was a weak relationship between utilization management initiatives and the quality of orders for thyroid tests. Conclusions: There is considerable practice variation in thyroid testing, which suggests a need for better guidance in test selection. Based on the current sample, some organizations could significantly improve the quality of thyroid testing and reduce testing costs.