Short-axis versus long-axis ultrasound-guided thyroid nodule biopsy: A randomized controlled trial of diagnostic performance in Iraq.

Background: Ultrasound guided fine needle aspiration cytology (US-FNAC) is the gold standard of evaluation of thyroid nodule. Two main approaches are available - short axis (perpendicular) and long axis (parallel), and each has theoretical clinical advantages. Evidence comparing the diagnostic performance of the two in Middle Eastern populations is limited. Objective: To compare the sensitivity, specificity, and accuracy of US-FNAC of short-axis versus long-axis in thyroid nodules with implications for patient care. Methods: A prospective multi-center randomized controlled trial was performed in Pioneer Private Laboratory and Mustafa Hafez Specialized Laboratory, Baghdad, Iraq from March to December 2024. A total of 196 nodules from patients ≥18 years were randomized to undergo short-axis or long-axis US-FNAC. Cytological results by the Bethesda System were correlated with histopathology. Sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were the primary outcomes. Results: Of 196 nodules (mean age 47.8 ± 13.5 years; 79.6 % female), patient and nodule characteristics did not differ between groups. Long-axis US-FNAC was 73.9 % sensitive, 100 % specific, 87.0 % accurate, 100 % positive predictive and 79.3 % negative predictive. Short-axis US-FNAC showed sensitivity of 76.7 %, specificity of 100 %, accuracy of 89.2 %, positive predictive value of 100 % and negative predictive value of 83.3 %. There were no differences in accuracy of diagnosis (p = 0.524). Conclusions: Short-axis and long-axis US-FNAC offer similar diagnostic performance of thyroid nodules in Iraqi patients. Although there were no differences in accuracy between procedures, operator experience, nodule characteristics, and patient factors could be used to choose the technique that best suited the clinical situation, which would allow for flexibility in clinical practice and potential improvements in patient comfort and procedural efficiency.