Fine-needle aspiration cytology of thyroid nodules--how well are we doing?

OBJECTIVES: To review the accuracy of fine-needle aspiration cytology in diagnosing non-toxic thyroid nodules and determine what factors are predictive of malignancy in patients with indeterminate cytology results.

DESIGN: Retrospective study.

SETTING: Regional hospital, Hong Kong.

PATIENTS: Patients with non-toxic thyroid nodules undergoing thyroidectomy from December 1999 to December 2003.

MAIN OUTCOME MEASURES: Sensitivity, specificity, positive and negative predictive value of fine-needle aspiration cytology, predictive factors for malignancy in patients with indeterminate fine-needle aspiration cytology results.

RESULTS: The sensitivity, specificity, positive predictive value, and negative predictive value of fine-needle aspiration cytology were 54%, 100%, 100%, and 75% respectively. For the 92 patients with fine-needle aspiration cytology reported as 'indeterminate for malignancy', aspiration cytology subgroup (P=0.005) and age (P=0.001) were significant risk factors for diagnosing malignancy.

CONCLUSIONS: Fine-needle aspiration cytology has high positive predictive value for thyroid cancer, enabling us to 'rule-in' malignant lesions with confidence. Among those with indeterminate fine-needle aspiration cytology, atypical cell lesions and age greater than 40 years conferred increased risk of malignancy.