Concordance Between Fine-Needle Aspiration Cytology and Histopathological Findings Among Thyroidectomy Patients at St. Paul’s Hospital Millennium Medical College, Addis Ababa, Ethiopia

Abstract

Abstract Background: Fine-needle aspiration cytology (FNAC) serves as the primary preoperative diagnostic tool for thyroid nodules, but its performance varies across settings due to differences in operator expertise, Bethesda classification implementation, and local disease patterns. In Ethiopia, where goiter remains endemic, institution-specific FNAC accuracy data against histopathology are limited. Objective: To evaluate the concordance between Fine-Needle Aspiration Cytology and postoperative histopathological findings among patients undergoing thyroidectomy at St. Paul’s Hospital Millennium Medical College. Methods: This retrospective diagnostic accuracy study included 400 consecutive patients who underwent thyroidectomy with available preoperative Fine-Needle Aspiration Cytology and postoperative histopathology results at St. Paul’s Hospital Millennium Medical College from January 2022 to December 2025. Data on demographics, clinical characteristics, ultrasound findings, and cytology and histopathology results were collected using structured checklists from electronic medical records. Statistical analyses were performed using IBM SPSS Statistics version 27. Diagnostic performance metrics including sensitivity, specificity, positive predictive value, and negative predictive value were computed. Cohen’s kappa coefficient was used to measure agreement between Fine-Needle Aspiration Cytology and histopathology. A p-value less than 0.05 was considered statistically significant. Results: A total of 400 patients undergoing thyroidectomy were analyzed (median age 39 years, IQR: 30–50; 90.3% female). FNAC diagnoses predominantly comprised Bethesda Category II (benign; 68.0%), Category IV (follicular neoplasm; 11.3%), and Category VI (malignant; 11.0%). After excluding non-diagnostic Category I (3.8%) and indeterminate Categories III/IV (13.1%) cases, diagnostic accuracy analysis of 331 patients revealed FNAC sensitivity of 73.6%, specificity of 96.9%, positive predictive value of 87.0%, and negative predictive value of 93.0%. Substantial agreement was observed between FNAC and histopathology for malignancy detection (Cohen's kappa = 0.764). Conclusion: FNAC shows good diagnostic accuracy in this Ethiopian cohort, particularly high specificity for ruling out malignancy, supporting its role as an effective triage tool. Keywords: Diagnostic accuracy; Fine-needle aspiration cytology; Postoperative biopsy; Thyroid nodules; Bethesda system; Ethiopia