Low or undetectable basal thyroglobulin levels obviate the need for neck ultrasound in differentiated thyroid cancer patients after total thyroidectomy and I-131 ablation.

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Low or undetectable basal thyroglobulin levels obviate the need for neck ultrasound in differentiated thyroid cancer patients after total thyroidectomy and I-131 ablation.

Thyroid. 2018 Apr 18;:

Authors: Verburg F, Maeder U, Giovanella L, Luster M, Reiners C

Abstract
BACKGROUND: Neck ultrasound (NUS) is currently seen as a main component of follow-up of differentiated thyroid cancer (DTC) and is usually performed regardless of non-stimulated thyroglobulin (Tg) levels. The aim of this study is to determine whether there is a clinical benefit from such a routine NUS in DTC patients.
METHODS: We performed a retrospective database study of 3176 cervical ultrasound exams performed in 773 patients between June 15, 1996 and July 1, 2012. The assessement of the accuracy of ultrasound results was assessed based on the results of further diagnostic and / or therapeutic procedures within 6 months of a particular ultrasound.
RESULTS: 2199 NUS exams were classified as true negative, 216 as true positive, 692 as false positive in 339 (43.9%) individual patients, 170 of whom were low risk, and 69 as false negative. Thus overall sensitivity, specificity, PPV, NPV and accuracy (95% confidence interval) were 75.8(70.1-81.5)%, 76.1(74.3-77.8)%, 23.8(18.1-29.5)%, 97.0(96.2-97.7)% and 76.0(74.3-77.7)%, respectively. No significant differences between low and high risk patients were found. There were no significant differences between patients with an undetectable and a low detectable (<1 µg/l) Tg level; these two groups however both showed significantly lower PPV and higher NPV than patients with a Tg ≥1 µg/l. From January 2007 onwards, true positive and false negative neck ultrasounds were no longer observed in patients with Tg <1 µg/l.
CONCLUSION: After total thyroidectomy and I-131 ablation, neck ultrasound should be reserved only for anti-Tg-antibody negative patients with a Tg level of ≥1 µg/l.

PMID: 29665748 [PubMed - as supplied by publisher]

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