Comparison between sensitivity and specificity of thyroid elastography and fine needle aspiration cytology in differentiating the nature of thyroid nodules
Authors: Allam Khalid Esmat , Madkour Sherihan Said , El-Ghitany Noha Abdelrahman 
Published: October 2021

Abstract

Background
Nodular goiter is the most frequent disease of the thyroid gland, it may affect up to 50% of adults and elderly people, Although malignancy only occurs in about 5% of thyroid nodules, the detection rate of papillary thyroid carcinoma has increased consistently both in women and men and in all ethnic groups Thus, the task of differentiating malignant from benign nodules is necessary. Ultrasound elastography (USE) is a non-invasive, completely painless for the patient and can be easily performed even during routine ultrasound examinations. It assesses lesion stiffness by evaluating tissue distortion in response to stress.

Objective
Study the role of strain elastography in the characterization of benign and malignant nature of the thyroid nodule Compare the sensitivity and specificity of ultrasound elastography (USE) and fineneedle aspiration cytology (FNAC) as preoperative predictor of malignancy in order to decrease the need for FNAC. Cytology report is the gold standard/ histopathology report if available.

Patients and Methods
Type of Study: Cross-sectional study. Study Setting: The study was conducted at Ain Shams University Hospitals. Patients: 32 patients, 16 benign, and 16 malignant Patients with thyroid nodules proven by FNAC referred to Ain Shams University Radiology Unit.

Results
After analysis of strain index (SI) and the elasto score with FNAC we found the cut of point for thyroid malignancy was &gt;1.4 and &gt;2 respectively. The sensitivity and specificity of strain index (SI) for thyroid malignancy diagnosis were 100% and 75%, respectively. The positive and negative predictive values were 80% and 100%, respectively its p-value was 0.000, being a highly significant test.The US-elastography score’s sensitivity and specificity for thyroid malignancy diagnosis both were 81.25%. The positive and negative predictive values both were 81.2%, its pvalue was 0.000, being a highly significant test. After the Postoperative histopathology which is done to only ten patients of the 32 patients with available results (31.3%), 4 of them were benign (12.5%), and six were malignant (18.8%), We conclude that the Elasto ratio is the most sensitive diagnostic test with NPP (negative predictive value) of 100 % being the best screening test while the FNAC is the most specific test with PPV(positive predictive value) of 100 % being the best diagnostic test while the elasto score’s p-value was 0.065, being a a non-significant test. Despite this good diagnostic performance, USE with SI assessment not yet meets all requirements for an optimal diagnostic tool as its specificity is only 75%, while that of FNAC is almost reaching 100% compared to the postoperative histopathology

Conclusion
Strain elastography was highlighted as a good tool for pre-operative differentiation of benign from malignant lesions showing high sensitivity and moderate specificity compared to other studies, thus further decreasing thyroid biopsies and surgeries. The most reliable tool in our study was the elasto ratio having the highest sensitivity. Ultrasound examination in combination with elastography is a well-tolerated, non-invasive, and cost-effective diagnostic tool in the pre-operative assessment of thyroid nodules, which is able to enhance the accuracy of assessing the risk of malignancy in thyroid nodules and for selecting nodules for FNAC, thus can be used to postpone the FNAC to decrease the amount of the unnecessary FNAC.