Background: In the US, thyroid stimulating hormone (TSH) is the 4th most commonly ordered laboratory test with thyroxine measurement being the 10th commonest. In 2016, Medicare alone spent $482 million on 21.5 million performed TSH tests and $12.28 million on 7.1 million performed thyroxine measurement tests. The objectives of this study were to analyze (a) the clinical utility and cost-effectiveness of inpatient TSH testing (b) the pattern of thyroid function tests (TFTs) ordered.
Methods: This is a single-centered retrospective study done on patients admitted to Medicine, Neurology and Psychiatry services at a tertiary care center between October 26,2015 to October 25,2018. Exclusion criteria were age <18 years and prior thyroid-related disorders. Based on TSH results, in relation to normal reference range, admissions were divided into 2 groups – normal and abnormal. Records of patient in abnormal group were extracted for chart review. Abnormal group was then divided into 2 sub-groups based on positive and no outcomes. Positive outcomes were defined when a diagnosis of overt or subclinical hypo/hyperthyroidism was made and (i) inpatient treatment was started and/or (ii) an appropriate endocrinology referral was made. No outcomes were defined when (i) subclinical or overt hypo/hyperthyroidism was diagnosed and no intervention was done or (ii) euthyroid sick syndrome was diagnosed or (iii) lack of above-mentioned positive outcomes.
We also calculated the number of bundled TFTs (bTFTs), defined as TSH testing done simultaneously with free T4 (fT4), total T3 (T3) or free T3 (fT3) tests. Patients with a prior abnormal TSH test in the same admission were excluded.
Results: Total of 24,243 TSH tests(t) were sent on 22,123 visits(n) to selected services, irrespective of history of thyroid disorder. Of these 17,628 (72.7%) tests were ordered in visits with no history of thyroid disorder (n = 16,129). 13,093 and 3,036 visits were flagged normal and abnormal, respectively (81.17% vs 18.83%). Total 136 (0.84%) visits resulted in a positive outcome (t=194; 1.1%). In regards to fT4, 4995 (96.63%) of 5169 tests resulted in no outcome. Over the 3-year period of study, of the 136 visits with positive outcome, only 54 had overt hypo/hyperthyroidism. Total 4,103 bTFTs (23.27% of total TSH tests) were sent as an initial screening test for thyroid disorder over the same period. Based on the 2016 National Limitation Amount, $153,467/year worth of thyroid-function tests (TFTs) were ordered at a single center resulting in no positive outcome.
Conclusions: Inpatient TFTs provide a low yield of true-positive results, overall low clinical utility, add to laboratory over-utilization and the rising health-care costs.
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