Diagnostic Value of Molecular Testing in Sonographically Suspicious Thyroid Nodules

Area of Science:

• Endocrinology
• Oncology
• Diagnostic Imaging

Background:

• Thyroid fine-needle aspiration biopsies yield indeterminate cytology in 20% of cases, necessitating further diagnostic refinement.
• Molecular testing offers a tool to improve diagnostic accuracy for indeterminate thyroid nodules.

Purpose of the Study:

• To assess the diagnostic accuracy of molecular testing, specifically the Afirma Gene Expression Classifier (GEC), in relation to ultrasound risk stratification.
• To compare the performance of GEC results across different ultrasound risk categories.

Main Methods:

• Retrospective analysis of 297 thyroid nodules with indeterminate cytology undergoing reflexive GEC testing.
• Nodules were classified using the American Thyroid Association (ATA) and American College of Radiology Thyroid Imaging, Reporting and Data System (TI-RADS) ultrasound risk categories.
• Diagnostic performance metrics (PPV, specificity) of GEC were compared across ATA ultrasound risk categories.

Main Results:

• Malignancy was confirmed in 22% of nodules.
• A suspicious GEC result was more frequent in high-suspicion ATA nodules (81%) versus other categories (57%; P=.04).
• The positive predictive value (PPV) of GEC was consistent across ATA categories (64% vs 48%; P=.39), while high-suspicion ATA classification demonstrated higher specificity (93%) than a suspicious GEC result (51%; P<.01).

Conclusions:

• Molecular testing's positive predictive value is consistent regardless of ultrasound risk category.
• A suspicious GEC result in high-suspicion nodules does not enhance diagnostic specificity.
• Ultrasound risk classification remains a crucial factor in managing indeterminate thyroid nodules.