Additive diagnostic value of liquid-based preparation and conventional smears in Bethesda I thyroid nodules

Objectives: Fine-needle aspiration (FNA) is crucial for evaluating thyroid nodules, traditionally using conventional smears (CSs). Recently, liquid-based preparations (LBPs) have gained popularity. This study compared CS and LBP accuracy, combined and separately, in reducing nondiagnostic (Bethesda I) results and identified predictors associated with Bethesda I for both methods combined and separately. Methods: A prospective comparison of thyroid FNA results in early 2024, using LBP alone vs LBP combined with CSs, was conducted. Retrospective data were collected from 2087 patients who underwent cytologic evaluation between 2020 and 2023, using CS alone and LBP combined with CSs. The study compared nondiagnostic results between the methods and adjusted for significant predictors. Results: In a prospective analysis of 218 LBP samples, combining CSs improved diagnosis in 15 cases (7%), allowing diagnosis in 12 and upgrading the result in 3 cases compared with LBP alone. In the retrospective analysis (CS, 1126 samples; LBP and CS, 961 samples), nondiagnostic results occurred in 14.2% and 18.2% of the cases, respectively (P = .793). Higher nondiagnostic results were significantly associated with older age, comorbidities, and pure cysts (P = .001) for both methods. For CS only, significant associations were found with abnormal thyroid-stimulating hormone (TSH) levels (P = .050), macrocalcifications (P = .045), and heterogeneous cysts (P = .038). Conclusions: We did not demonstrate an additive effect for the LBP method. However, it may still be preferable in nodules with abnormal TSH levels, heterogeneous cystic features, or macrocalcifications. The prospective findings indicate a clinical advantage for CS analysis. Accordingly, we recommend performing aspiration for both techniques, using CS only if a nondiagnostic result is obtained for LBP.