Diagnostic Accuracy of Ultrasonography in Differentiating Benign and Malignant Thyroid Nodules Using Fine Needle Aspiration Cytology as the Reference Standard

Background: In Pakistan thyroid cancer is responsible for 1.2% cases of all malignant tumors. Ultrasonography(US) is helpful in detecting cancerous thyroid nodules on basis of different features like echogenicity, margins,microcalcifications, size, shape and abnormal neck lymph nodes. We therefore aimed to calculate diagnosticaccuracy of ultrasound in detection of carcinoma in thyroid nodules taking fine needle aspiration cytology asthe reference standard. Materials and
Methods: A cross-sectional analytical study was designed to prospectivelycollect data from December 2010 till December 2012 from the Department of Radiology in Aga Khan UniversityHospital, Karachi, Pakistan. A total of 100 patients of both genders were enrolled after informed consent viaapplying non-probability consecutive sampling technique. Patients referred to Radiology department of AgaKhan University to perform thyroid ultrasound followed by fine-needle aspiration cytology of thyroid noduleswere included. They were excluded if proven for thyroid malignancy or if their US or FNAC was conductedoutside our institution.
Results: The subjects comprised 76 (76%) females and 24 males. Mean age was 41.8±SD12.3 years. Sensitivity and specificity with 95%CI of ultrasound in differentiating malignant thyroid nodulefrom benign thyroid nodule calculated to be 91.7% (95%CI, 0.72-0.98) and 78.94% (0.68-0.87) respectively.Reported positive predictive value and negative PV were 57.9% (0.41-0.73) and 96.8% (0.88-0.99) and overallaccuracy was 82%. Likelihood ratio (LR) positive was computed to be 4.3 and LR negative was 0.1.
Conclusions:Ultrasonography has a high diagnostic accuracy in detecting malignancy in thyroid nodules on the basis offeatures like echogenicity, margins, micro calcifications and shape.