Background: Lymphocytic thyroiditis is the most common form of subclinical and overt hypothyroidism in an iodine sufficient region. It is the present manifestation of thyroid diseases in the post iodization era. The aim of this study is to validate the Doppler findings in lymphocytic thyroiditis

Materials and Methods: Diagnostic test evaluation was done by comparing the Doppler findings with fine needle aspiration cytology which is taken as the reference standard. 89 patients with diffuse neck swelling in the age group 18-80 years, who came for sonographic examination of the thyroid to the Department of Radiodiagnosis, Government TD Medical college Alappuzha were assessed.

Result: The Doppler findings in the study were classified into three patterns and found that 68% of patients with pattern 2 and pattern 3 had lymphocytic thyroiditis. A new cut off value for Resistive Index was calculated by plotting. Receiver operating Characteristic curve.

Conclusion: The sensitivity, specificity, PPV and NPV of increased vascularity (pattern 2&3) in diagnosing lymphocytic thyroiditis was found to be 71%, 52%, 80% and 48% respectively. Diagnosing lymphocytic thyroiditis by pattern 3 vascularity had a high specificity and positive predictive value of 88 and 91 respectively. A new cut off value of RI was identified as 0.61 with a sensitivity of 78% and specificity of 65% from the ROC curve.

Keywords-Colour Doppler, Resistive index, Lymphocytic Thyroiditis, Spectral pattern.