A study to determine the 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, and they are noted in patients referred to the University Teaching Hospital (UTH) and Ndola Central Hospital (NCH), which are tertiary-level hospitals in Lusaka and Ndola respectively. 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 UTH and NCH in order to establish a basis for introducing its use in the management of thyroid nodules at the two institutions. Objectives To evaluate the accuracy of FNAC, as compared to histopathology, in the diagnosis of thyroid nodules at UTH and NCH. 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. A structured questionnaire was used to gather information from the patient and record files. FNAC was then performed on the thyroid nodules pre-operatively by either the author or the two assistants. 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 peak age of incidence was in 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 v 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 of 83.33%, 89.09%, 94.23 and 71.42% respectively. Conclusion In this study FNAC of thyroid nodules at UTH and NCH had a high sensitivity, specificity, and predictive value, and can therefore be recommended to be adopted as a pre-operative tool for screening of thyroid nodules. The study also demonstrated that most of the thyroid nodules were benign, while follicular carcinoma was the commonest malignancy followed by papillary carcinoma.