Are thyroid function tests too frequently and inappropriately requested?

Abstract

In spite of data supporting the use of the serum thyrotropin (TSH) concentration as the best test to detect abnormal thyroid function, measurement of circulating thyroid hormones with or without a serum TSH continues to be frequently requested to evaluate thyroid function. We have analyzed how combinations of thyroid function tests were ordered by referring physicians and the results of the tests in order to offer some suggestions as to how to use thyroid function tests in a cost effective manner. During 1995, 19,181 inpatient and outpatient requests (45,865 different tests) for thyroid function tests were received by the laboratory of a 1600 bed University Hospital in Parma, Italy. The following tests were carried out: T4, free T4, T3, free T3 and TSH. Serum TSH values below and above the normal range were considered to reflect abnormal thyroid function i.e. hyperthyroidism, or hypothyroidism including subclinical disease independent of the results of the other tests. Combinations of ordered tests and the percent of the total for each combination were: TSH+T4+T3 (56%), TSH+FT4+FT3 (14%), TSH (12%), TSH+FT4 (9%), TSH+T4 (1%), TSH+T4+T3+FT4+FT3 (5%), others (3%). The T4+T3+TSH panel (10,780 requests) had normal serum TSH values in 80.6% and the FT4+ FT3+TSH panel (2,590 requests) had normal TSH values in 73.2%. Elevated serum TSH concentrations were observed more frequently in hospitalized than in ambulatory patients (9.7% vs 7.4% p<0.001). T3 (elevated serum T3, normal T4 and low TSH concentrations) and T4 (elevated serum T4, normal T3 and low TSH concentrations) toxicosis were observed in 8.1% and 9.4%, respectively, of the requested test (NS). FT3 and FT4 toxicosis, defined as for T3 and T4 toxicosis, were observed in 7.5% and 4.9%, respectively (NS). The low T3 and low FT3 syndrome in hospitalized patients was present in 1.6% and 2.3% of the requests, respectively (NS). The low T4+low T3 and low FT4+low FT3 syndrome was present in only 0.3% and 0.2%, respectively, of the requests. Our study shows that a) in hospitalized patients thyroid function tests were requested in 20% of the patients and only one in 14 of these patients at the highest could have abnormal thyroid function, as indicated by abnormal TSH value b) FT4 (or T4) is as useful as FT3 (or T3) in the diagnosis of hyperthyroidism, c) in hospitalized patients the low T3 syndrome was far less common than that reported in the literature, probably due to the lower severity of illness, d) panels which include T3 and FT3 are not justified, and e) serum TSH alone is the most appropriate initial thyroid function test.

Are we using Thyroid Function Tests Appropriately?

“…The various studies done to evaluate the ordering pattern of thyroid function tests indicate that frequency of order of TFT is much higher than that of only TSH [11][12][13]. Similar studies have not been reported from India.…”

Medical stewardship: Pathology evidence based ordering to reduce inappropriate test ordering in a teaching hospital

“…[4] The National Coalition of Public Pathology [4] (p5) defined inappropriate pathology as requests "performed at the wrong time or too frequently to be of value in diagnosis, prognosis, or ongoing clinical management". Appropriateness has included concerns associated with common tests such as Full Blood Count (FBC), [5] Liver Function Tests (LFTs), [6] Vitamin B 12 /folate (B 12 ), [7] Thyroid Function Tests (TFTs), [8] Vitamin D (Vit D), Prostate-Specific Antigen (PSA), and Troponin. [9] This issue is compounded in teaching hospitals, because the least experienced medical officers; interns and residents order the majority of tests.…”

The clinical utility and cost effectiveness of routine thyroid screening in adult psychiatric patients presenting at Stikland Hospital, Cape Town, South Africa

“…5,10 In most studies, the yield of abnormal thyroid test results however remains low. Psychiatric clinicians should be aware that thyroid test abnormalities do not always denote thyroid disease and that the proper interpretation of test results is dependent on a good basic understanding of thyroid physiology and the methodology of the test.…”