Low Value of Thyroid Testing in the Pediatric Inpatient Setting

Our objective was to assess the frequency of pediatric inpatient thyroid testing, frequency of detection of abnormal results, and apparent impact on patient management.

This is a retrospective study of admissions from July 2015 to June 2016 at a large urban children's hospital. Chart review was conducted on all hospitalized pediatric patients who underwent thyroid testing. We used a normal range of 0.5 to 5.0 μIU/mL for thyroid-stimulating hormone (TSH) and 1.0 to 2.0 ng/dL for free thyroxine (FT4), except for neonates for whom we used the higher reference ranges specified by the hospital laboratory.

Thyroid testing occurred in 1202 (5.7%) of 20 907 hospitalizations; 79.3% had combined thyroid function tests (TFTs) with TSH + FT4 being most common, and 20.6% had TSH only. Combined TFTs were ordered routinely by psychiatry and frequently by endocrine, gastrointestinal, cardiology, and neurology services, but many cases had no identified reason for testing. Of the 205 abnormal tests (17.1%), the most common abnormalities in the combined TFTs group were normal FT4 and increased TSH (35.4%) (76% of which were between 5 and 10 μIU/mL), normal FT4 and TSH 0.1 to 0.5 μIU/mL (33.1%), and high FT4 but normal TSH (14.3%). Patients with new-onset type 1 diabetes had borderline low or high TSH in about 20% of cases, but all abnormalities resolved at outpatient follow-up. Overall, 8 patients (0.66%) were started on levothyroxine.

Pediatric inpatient thyroid testing is relatively common at our institution, and although results are often abnormal, they do not point to thyroid disease that has contributed to the reason for hospitalization and do not identify patients in urgent need of starting therapy.