Two-step thyroid screening strategy in the critical patient

Background: Thyroid function biochemical tests are known for their usefulness in prognosis of long-term critical patients, although current data are controversial regarding the clinical benefit of both free triiodothyronine and thyroxine as prognostic thyroid markers during the first 48 h after Intensive Care Unit (ICU) admission. Methods: The aim of this study was to evaluate the usefulness of two strategies for thyroid function assessment in the first 48 h after admission at the ICU. The usefulness of a two-step biochemical thyroid strategy (initial isolated TSH determination, followed by subsequent fT(4) and fT(3)) was compared with a complete one-step biochemical profile (TSH + fT(4) + fT(3)). Results: No significant differences were found between the rates of thyroid dysfunction detection when using both strategies (2.8% vs. 2.4%; p = 0.71). Using the two-step strategy and a 2.5 mu UI/mL cut-off value for TSH, sensitivity and negative predictive value were 100%. Among patients with an altered fT(3) only, mortality was 14% if TSH <= 2.5 mu UI/mL, whereas it was 7% if TSH > 2.5 mu UI/mL (p = 0.008). Conclusions: For patients with critical illness, the early two-step thyroid screening strategy (starting with an isolated TSH determination between 24 and 48 h after admission) led to a saving of 50% in fT(4) and fT(3) tests, with a false-negative rate of 1.3%. This represents an improved diagnostic approach, hence avoiding the performance of unnecessary complementary biochemical measurements. (C) 2016 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.