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Ultrasound elastography accurately predicted thyroid malignancy
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Ultrasound elastography appeared to accurately predict the malignancy of thyroid nodules, a recent research paper suggests.
“An accurate assessment of the elastographic [strain index] owns an excellent diagnostic performance in predicting malignancy of thyroid nodules. A coexistent autoimmune thyroid disease does not hamper its diagnostic performance, which is higher than that provided by any conventional US sign of malignancy,” Flavia Magri, MD, PhD, of the unit of internal medicine and endocrinology at Fondazione Salvatore Maugeri IRCCS; University of Pavia, Italy, and colleagues wrote. “Our findings provide a strong answer to some open questions regarding the role of ultrasound elastography in the diagnostic work up of thyroid nodules.”
The prospective study evaluated 661 thyroid nodules in 528 patients. The researchers conducted fine-needle aspiration cytology and ultrasound elastography in their evaluations of the samples, which were categorized into five groups:
- THY1 (nondiagnostic);
- THY2 (benign);
- THY3 (indeterminate follicular lesion);
- THY4 (suspicious for malignancy) and
- THY5 (malignant).
“Patients bearing the THY4/THY5 nodules were significantly younger (median age: 49 vs. 57 years, P=.01), had slightly higher median serum levels of [thyroid-stimulating hormone] than patients bearing THY2 nodules (median TSH=2.1 mIU/L vs. 1.7 mIU/L) and their nodules were significantly smaller when evaluated as maximum diameter (median maximum diameter=13.05 vs. 17.9, P=.001),” researchers wrote.
The mean ultrasound elastographic strain index value was significantly greater among THY4/THY5 nodules vs. THY2 nodules in the presence of autoimmune thyroid disease-positive (3.35 vs. 2.30, P=.002), autoimmune thyroid disease-negative (4.13 vs. 2.14, P=5.87×10-8), and autoimmune thyroid disease-unknown patients (3.45 vs. 2.14, P=8.3×10-4), according to data.
In addition, a strain index cutoff value of ≥2.905 was linked to a significantly greater prediction of the nodule being malignant in both screening and replication sets, researchers wrote.
Further studies are warranted to determine the diagnostic value of ultrasound elastography in THY3 nodules. If its accuracy is confirmed, researchers wrote that fine-needle aspiration cytology could be avoided.
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Jennifer Sipos, MD
Ultrasound elastography is a technology that holds much allure in the evaluation of thyroid nodules. There are conflicting reports of its accuracy and reproducibility though, limiting its use in clinical practice thus far. The study by Magri and colleagues sought to evaluate one of the biggest shortcomings, its efficacy in patients with autoimmune thyroid disease (ATD). The authors have clearly demonstrated that the strain index is significantly different between benign and malignant nodules in patients with ATD. Further, they established that strain index performed as well or better than traditional ultrasound features associated with an increased risk of malignancy. Unfortunately, the translation of these results into clinical practice is limited, as patients with indeterminate nodules were excluded from the analysis.
Another constraint with ultrasound elastography is the concern for interobserver variability. While utilization of strain index has mitigated this point somewhat, it is important to note that the authors advise each operator to calculate his or her own institutional cut-off value for the strain index because of its “intrinsic observer dependency.”
In conclusion, the present study by Magri and colleagues is a careful analysis of the accuracy of elastography; the authors have successfully determined that elastography is a useful adjunct to the ultrasonographic assessment of thyroid nodules, even in patients with ATD. Further study of patients with all cytological diagnoses (including indeterminate cytology) is needed to determine if the strain index can distinguish benign from malignant nodules. At the present time, however, elastography remains just one of many tools in the arsenal to evaluate thyroid nodules and does not supersede the need for fine needle aspiration.
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