Strain ratio ultrasound elastography increases the accuracy of colour-Doppler ultrasound in the evaluation of Thy-3 nodules. A bi-centre university experience

Objectives To assess whether ultrasound elastography (USE) with strain ratio increases diagnostic accuracy of Doppler ul- trasound in further characterisation of cytologically Thy3 thy- roid nodules. Methods In two different university diagnostic centres, 315 patients with indeterminate cytology (Thy3) in thyroid nod- ules aspirates were prospectively evaluated with Doppler ul- trasound and strain ratio USE before surgery. Ultrasonograph- ic features were analysed separately and together as ultra- sound score, to assess sensitivity, specificity, positive predic- tive value (PPV) and negative predictive value (NPV). Re- ceiver operating characteristic (ROC) curves to identify opti- mal cut-off value of the strain ratio were also provided. Diag- nosis on a surgical specimen was considered the standard of reference. Results Higher strain ratio values were found in malignant nodules, with an optimum strain ratio cut-off of 2.09 at ROC analysis. USE with strain ratio showed 90.6 % sensitivity, 93 % specificity, 82.8 % PPV, 96.4 % NPV, while US score yielded a sensitivity of 52.9 %, specificity of 84.3 %, PPV 55.6 % and NPV 82.9 %. The diagnostic gain with strain ratio was statistically significant as proved by ROC areas, which was 0.9182 for strain ratio and 0.6864 for US score. Conclusions USE with strain ratio should be considered a useful additional tool to colour-Doppler US, since it improves characterisation of thyroid nodules with indeterminate cytology. Key points • Strain ratio measurements improve differentiation of thyroid nodules with indeterminate cytology • Elastography with strain ratio is more reliable than ultra- sound features and ultrasound score • Strain ratio may help to better select patients with Thy 3 nodules candidate for surgery