Thyroid testing in acutely ill patients may be an expensive distraction

Abstract

In health, an efficient negative feedback mechanism maintains serum thyroid hormone concentrations within an exquisitely controlled narrow range. Therefore any change that occurs to thyroid hormones in intrinsic thyroid disease is concordant and easy to interpret. Optimal functioning of the many tissues they influence is thereby facilitated. The situation in acute illnesses is different. Mechanisms that operate in these circumstances influence the hypothalamic-pituitary-thyroid axis and its components producing thyroid test results, which are discordant, do not fit recognizable patterns and are difficult to interpret. The yield of abnormalities is also low (about 7%). As many studies indicate, thyroid tests are expensive and consume large amounts of the hospital budget and resources of hospital laboratories. Other studies have shown that when abnormalities are detected, clinicians do not intervene or follow up these subjects. Therefore the clinical utility of thyroid testing in acutely ill patients is debatable. Interventions to change requestor behaviour with regard to thyroid testing in acutely ill subjects and the success of some audit and educational interventions are worthy of note. Thyroid testing in acutely ill patients is often an expensive distraction and is of limited clinical value. Targeted thyroid testing should be offered in this group only to those with: (a) symptoms or signs of thyroid disease e.g. goiter or orbitopathy; (b) risk factors for thyroid disease, previous or family history of thyroid disease; (c) taking drugs which potentially affect thyroid function e.g. thyroxine replacement therapy, amiodarone, lithium, mechanistic target of rapamycin (mTOR) inhibitors, interferon, alemtuzumab etc; (d) unexplained tachydysrhythmias.

Things We Do for No Reason™: Routine Thyroid-Stimulating Hormone Testing in the Hospital

“…In addition, cultural norms may encourage the routine assessment of thyroid function as a part of a thorough inpatient evaluation, even when alternative diagnoses could explain the patient's symptoms. 8 In many hospitals, TSH is included in emergency department laboratory panels and hospital admission order sets (sometimes as a preselected default), which can significantly influence prescriber ordering. 4,6,7,9 Hardwick et al conducted structured interviews with primary care providers to explore the factors contributing to high thyroid testing variability.…”

“…Although the prevalence of unrecognized thyroid disease in hospitalized patients is 1%-2.5%, 11 NTIS is observed in up to 62% of hospitalized patients and not exclusively in critically ill patients as previously thought. 8 Risk factors include infection, stroke, myocardial infarction, kidney or liver injury, burns, malnutrition, malignancy, and recent surgery, as well as multiple medications. 12 Contributing factors may include the effect of cytokines on thyroid-releasing hormone and TSH secretion, decreased deiodinase activity, and changes in thyroid hormone receptor activity.…”

“…12 Contributing factors may include the effect of cytokines on thyroid-releasing hormone and TSH secretion, decreased deiodinase activity, and changes in thyroid hormone receptor activity. 8 No one pattern of thyroid function testing is pathognomonic of NTIS. 8,12 The high prevalence of NTIS reduces the specificity of TSH testing in hospitalized patients.…”

“…8 No one pattern of thyroid function testing is pathognomonic of NTIS. 8,12 The high prevalence of NTIS reduces the specificity of TSH testing in hospitalized patients. In this population, Attia et al determined that mild abnormalities (TSH 0.1-0.6 mIU/L or 6.7-20 mIU/L) have a positive likelihood ratio (LR+) of true thyroid disease of 0.0 and 0.74, respectively, counterintuitively reducing rather than increasing the posttest probability of thyroid disease.…”

“…19 The specificity of TSH testing in the hospital setting is too low to justify screening for mild or subclinical disease. 8 Instead, directed thyroid function testing should be performed for hospitalized patients with sufficient signs and symptoms to raise the pretest probability of a clinically relevant result (Table). According to Attia et al, the total number of signs and symptoms (rather than one particular sign or symptom) may be the most reliable indicator.…”