Reliability of k-tirads in evaluation of thyroid nodules: comparison with fnac in patients referred for thyroid ultrasound at Muhimbili tertiary hospitals

Abstract

Background: Thyroid nodules are relatively common worldwide with a malignancy potential in 5%. Studies show prevalence of nodules in up to 68% of the population using Ultrasound (USS). Recent studies have revealed that USS features can be used to screen for thyroid malignancy without necessity for biopsy in every thyroid nodule. Korean Thyroid Imaging Reporting and Data System (K-TIRADS) is among the modified sonographic risk stratification system for thyroid nodules which makes use of greyscale USS findings regardless of clinical information. We assessed the reliability of K-TIRADS in predicting the nature thyroid nodules using Fine Needle Aspiration Cytology (FNAC) as Gold standard in patients referred for thyroid USS at Muhimbili National Hospital (MNH) and MUHAS Academic Medical Center (MAMC) from October 2018 to April 2019. Objective: To determine the reliability the Korean Thyroid Imaging Reporting and Data System (K-TIRADS) in evaluation of thyroid nodules in patients referred for thyroid ultrasound at Muhimbili Tertiary hospitals from October 2018 to April 2019. Methodology: This was a cross sectional hospital based study which involved 96 Patients with thyroid nodules referred to Imaging Department for thyroid Ultrasound at MNH and MAMC. Data collection was done using a structured questionnaire filled by the principal investigator. Thyroid ultrasound was performed and imaging findings reported by the Principal Investigator, confirmed by a radiologist. In case of disagreement a second radiologist was consulted and the conclusion was reached by consensus. K-TIRADS categories for each nodule were then determined. FNAC was done by pathologist for palpable nodules. For non palpable nodules the Principal Investigator and pathologist collaborated under USS guidance to take the samples. Smears for FNAC were prepared and interpreted by the Pathologist. Ultrasound findings were compared with cytology results as the ―Gold standard‖. Statistical Package for Social Sciences (SPSS) version 23 was used for data analysis. Sensitivity, Specificity, Positive and Negative predictive values and malignancy risk of K-TIRADS were determined. X 2 test was used for inferential statistics of categorical variables. Spearman’s rank correlation test was used to assess the relationship between categories of K-TIRADS and v Cytology results. A p value of less than 0.05 was considered significant at 95% confidence level. Results: Majority of participants were females with Male to female ratio 1:8. The age range was from 6 to 92 years .The rate of malignancy was higher in the >40 age group. The risk of malignancy for K-TIRADS 2, 3, 4 and 5 were 0%, 3.8%, 44.1% and 100% respectively. Using K-TIRADS 3(for nodules ≥1.5cm) , K-TIRADS 4 and K-TIRADS 5 as criteria for malignancy the Sensitivity, Specificity, Positive Predictive Value(PPV) and Negative Predictive Value ( NPV) a were 100%, 42.7%, 12.1% and 100% respectively. Conclusion: Females constitute the majority of thyroid nodule patients. Age above 40 years is a risk for thyroid malignancy. Majority of thyroid nodules are in K-TIRADS 3 category. Malignancy risk increases with the order of K-TIRADS category. K-TIRADS criteria demonstrates a very high sensitivity for thyroid malignancy and therefore a reliable screening tool. Recommendation: Patients with thyroid nodules can undergo ultrasound assessment using K TIRADS as the first modality. Patients diagnosed with benign thyroid nodules using K TIRADS may not need further invasive screening (e.g FNAC). A community based study with a large sample is suggested to obtain more evidence for implementation of K-TIRADS.