COMPARISON OF ELASTOGRAPHIC STRAIN INDEX AND THYROID FINE-NEEDLE ASPIRATION CYTOLOGY IN 631 THYROID NODULES.

Context:Ultrasound (US) elastography (USE) was recently reported as a sensitive, non-invasive tool for identifying thyroid cancer. However, the accuracy of this technique is hampered by the intra- and inter- operator variability, some US features of the nodule and by the coexistence of autoimmune thyroid disease (ATD).Objectives:to assess the accuracy of USE in the differential diagnosis of thyroid nodules as compared with other US features, to evaluate its feasibility in the presence of ATD, to identify the strain index (SI) cut-off with the highest diagnostic performance.Design:528 consecutive patients for a total of 661 thyroid nodules were evaluated. All nodules underwent fine-needle aspiration cytology (FNAC) and USE evaluation. The SI was calculated as a ratio of the nodule strain divided by the strain of the softest part of the surrounding normal tissue.Results:The median SI value was significantly higher in THY4 and THY5 than in THY2 nodules in ATD-positive, ATD-negative and ATD-unknown patients. The cut-off of SI for malignancy was estimated at 2.905 by ROC curve analysis in a screening set (379 FNAC results), and then tested in a replication set (252 FNAC results). In all cases, a SI ≥ 2.905 conferred to the nodule a significantly greater probability of being malignant. This SI cut-off had the greatest AUC, sensitivity and NPV, compared to the conventional US features of malignancy.Conclusion:The elastographic SI has a high sensitivity, specificity and negative predictive value for the diagnosis of thyroid malignancy both in the presence and in the absence of ATD. If our data on USE will be confirmed also in THY3 nodules, FNAC could be avoided in a consistent number of thyroid nodules