Validation of a Decision Rule for Selective TSH Screening in Atrial Fibrillation

Abstract

IntroductionAtrial fibrillation (AF) is the most common cardiac dysrhythmia. Current guidelines recommend obtaining thyroid-stimulating hormone (TSH) levels in all patients presenting with AF. Our aim was to investigate the utility of TSH levels for emergency department (ED) patients with a final diagnosis of AF while externally validating and potentially refining a clinical decision rule that recommends obtaining TSH levels only in patients with previous stroke, hypertension, or thyroid disease.MethodsWe conducted a retrospective, cross-sectional study of consecutive patients who presented to an ED from January 2011 to March 2014 with a final ED diagnosis of AF. Charts were reviewed for historical features and TSH level. We assessed the sensitivity and specificity of the previously derived clinical decision rule.ResultsOf the 1,964 patients who were eligible, 1,458 (74%) had a TSH level available for analysis. The overall prevalence of a low TSH (<0.3μIU/mL) was 2% (n=36). Elevated TSH levels (>5μIU/mL) were identified in 11% (n=159). The clinical decision rule had a sensitivity of 88.9% (95% CI [73.0–96.4]) and a specificity of 27.5% (95% CI [25.2–29.9]) for identifying a low TSH. When analyzed for its ability to identify any abnormal TSH values (high or low TSH), the sensitivity and specificity were 74.4% (95% CI [67.5–80.2]) and 27.3% (95% CI [24.9–29.9]), respectively.ConclusionLow TSH in patients presenting to the ED with a final diagnosis of AF is rare (2%). The sensitivity of a clinical decision rule including a history of thyroid disease, hypertension, or stroke for identifying low TSH levels in patients presenting to the ED with a final diagnosis of atrial fibrillation was lower than originally reported (88.9% vs. 93%). When elevated TSH levels were included as an outcome, the sensitivity was reduced to 74.4%. We recommend that emergency medicine providers not routinely order TSH levels for all patients with a primary diagnosis of AF. Instead, these investigations can be limited to patients with new onset AF or those with a history of thyroid disease with no known TSH level within three months.

Thyroid testing in acutely ill patients may be an expensive distraction

“…Education of nurses, junior doctors and senior physicians in the futility of thyroid testing during acute illness, helps in reducing the number of tests done, as has been shown in two recent studies ( 34 , 38 ). Efforts should be made to devise a sensible, logical and easily understood set of guidelines for targeted thyroid testing in acutely ill patients in hospital medical assessment units ( 39 ).…”

Src-homology domain 2 containing protein tyrosine phosphatase-1 (SHP-1) directly binds to proto-oncogene tyrosine-protein kinase Src (c-Src) and promotes the transcriptional activation of connexin 43 (Cx43)

“…With the increase in age, the prevalence of AF increases sharply, from about 1% of the general population to about 10% of people over 80 years old [ 1 , 2 ]. At present, millions of patients are affected by AF that is expected to triple by 2050 [ 3 ]. AF can easily lead to thrombosis and increased ventricular rate, which is the main cause of embolic stroke.…”

The risks of defensive (emergency) medicine. The laboratory perspective

“…22 Decreased (i.e., <0.3 U/mL) and enhanced (>5 U/mL) TSH values could only be observed in 2 and 11% of patients, respectively, thus confirming that TSH measurement may not be cost-effective in the ED. 22 More recently, Giacomini and colleagues assessed the clinical usefulness of TSH test requests performed in patients admitted to ED, 23 and also found that elevated and decreased TSH values were only present in 3 and 1.2% of the patients, respectively. In only one patient displaying an increased TSH value the measurement of this biomarker led to a substantial change of the clinical decision making due to the presence of Hashimoto thyroiditis.…”