Diagnostic accuracy of fine needle aspiration puncture for diagnosing differentiated thyroid cancer

Abstract

INTRODUCTION: The importance of thyroid nodules (NT) lies in the need to exclude thyroid cancer,
which occurs in 7 to 15% of cases. In Argentina it represents 2.2% and 0.5% of all cancers that occur
annually in women and men respectively. NT fine needle aspiration (PAAF) cytology estimates the risk of
malignancy and is the confirmatory test for diagnosis, with a specificity of 94%.
OBJECTIVE: To determine the diagnostic accuracy of the cytopathological criteria of the BS obtained by
TN FNA for the diagnosis of thyroid cancer. To establish the frequency of each BS category in our
population. To alculate the percentage of malignancy for each category of the BS in our population.
PATIENTS AND METHODS: Observational, retrospective, diagnostic test study in which adult patients
with ultrasound suspicious for malignancy TN and FNA were included. Data of patients who underwent
thyroid surgery between January 1, 2012 and December 31, 2018 at the Reina Fabiola University Clinic in
Córdoba City were analyzed. Sensitivity, specificity, positive and negative predictive values of the
cytopathological criteria of the BS obtained by FNA were evaluated, taking as a gold standard the
pathological result.
RESULTS: 191 patients were included. 82.20% were female and the mean age was 43.45 ± 13.29. 89
patients were diagnosed of thyroid cancer, all of them classified as differentiated thyroid carcinoma (DTC).
Regarding the percentages of malignancy in the different categories of the Bethesda system, the rates of
malignancy for categories II, III, IV and V were 18.5%; 31.6%; 62.8% and 90.5%, respectively. Regarding
the performance of the Bethesda system, when analyzing its usefulness as a screening test (analysis 1:
category II vs. IV + V + VI) we found a sensitivity to detect malignancy of 84.6%, with a specificity of
72.6% , a PPV of 76.7%, a NPV of 81.5% and a global diagnostic accuracy of 78.8%. This analysis, in
highly suspicious punctures (analysis 2: category II vs. V + VI), increased the diagnostic accuracy of the
test to 85.2%, sensitivity 76.5%, specificity 93%, PPV 90.7% and NPV 81.5%.
CONCLUSIONS: The diagnostic accuracy of the BS used for the cytopathological evaluation of the risk
of malignancy in the FNA of thyroid nodules is good, which is why it is one of the recommended methods
in the diagnostic algorithm of thyroid cancer.