Diagnostic Accuracy of Fine needle Aspiration Cytology of Thyroid Nodules at two tertiary Hospitals in Zambia: a cross-sectional study

Abstract

Introduction: Thyroid nodules are one of the common surgical presentations in Africa and are of great concern because of their potential to be malignant. Zambia is not excluded from these common surgical conditions. However, there are no pre-operative cellular or intra-operative tissue diagnoses of the thyroid nodules done before thyroidectomy making it difficult to plan for an optimal and definitive management. Fine needle aspiration cytology (FNAC) is known to play a pivotal role in the screening and management of thyroid swellings. This study serves to assess the diagnostic accuracy of FNAC on thyroid nodules in patients at two tertiary hospitals in Zambia in order to establish a basis for introducing its use in the management of thyroid nodules at the institutions. Objectives: To evaluate the accuracy of FNAC, as compared to histopathology, in the diagnosis of thyroid nodules at University Teaching Hospital (UTH) and Ndola Central Hospital (NCH) in Zambia. Methods: This was a prospective cross-sectional study conducted in UTH and NCH surgery department from June 2014 to March 2015. Seventy-three patients, who presented with palpable thyroid nodules and underwent thyroidectomy, were enrolled in the study. The FNAC diagnosis of the patients was compared to the histopathology finding following thyroidectomy. Results: Females made up the majority of the patients (n=67, 91.8%). The ages of the patients ranged from 18 to 78 years. The mean age was 44.3 years and the peak age of incidence was in the fourth decade. All patients were clinically euthyroid at the time of enrolment. The FNAC findings included 23 cases reported as unsatisfactory (31.5%); 29 cases benign (39.7%); 2 cases atypical (2.7%); 6 cases suspicious (8.2%); and 13 cases malignant (17.8%). Histopathology findings were available from all 73 tissue samples of participants, of which 55 (75.3%) and 18 (24.7%) were reported as benign and malignant respectively. Of the 18 malignant cases identified by histology, the most common cancer was follicular carcinoma (n=9, 50%), followed by papillary carcinoma (n=6, 33.3%) and undifferentiated carcinoma (n=3, 16.7%). FNAC, in this study, had sensitivity, specificity, negative and positive predictive values, and accuracy of 83.33%, 89.09%, 94.23 and 71.42%, and 87.67% respectively. Conclusion: In this study, FNAC of thyroid nodules had a high sensitivity, specificity, predictive values and accuracy, and can therefore be recommended to be adopted as a pre-operative tool for screening of thyroid nodules.