BACKGROUND: Thyroid nodules carry a substantial risk of malignancy. Ultrasound and fine needle aspiration cytology (FNAC) are the most important investigations used to risk-stratify such lesions. The performance of these tests is a scarcely researched area in Ethiopia. The main objective of this study was to assess the diagnostic performances of ultrasound and FNAC in identifying thyroid cancers, using final surgical pathology as the reference standard.

METHODS AND MATERIALS: A paired comparative diagnostic accuracy study using retrospective data was conducted at Tikur Anbessa Specialized Hospital and Lancet General Hospital. The collected data were analyzed using SPSS Windows version 21, Microsoft Excel 2019, and diagnostic accuracy–calculating spreadsheets.

RESULTS: Two hundred and sixty-six (266) cases were included in the analysis. Of these, 204 (76.7%) were females. The median age (in years) was 45.0 (IQR = 20.0). McNemar’s test determined that the proportion of malignant lesions was statistically significantly different between the two tests (P < 0.001). Binary logistic regression models showed that the combination of ultrasound and FNAC had higher diagnostic performance metrics than the two tests used separately.

CONCLUSION: The study showed that FNAC outperforms ultrasound in diagnosing thyroid cancer. Thyroid ultrasound has higher sensitivity but significantly lower specificity than FNAC. This is an important and advantageous characteristic of a triaging test, but with a significant limitation as a rule-in test. Knowing the diagnostic performances of these tests greatly helps in triaging and clinical decision-making in the evaluation of individuals for thyroid cancer.

KEYWORDS: Thyroid nodules, Goiter, Thyroid cancer, Ultrasound, Cytology, Diagnostic accuracy