Diagnostic accuracy of fine needle aspiration cytology of the thyroid: impact of ultrasonography and ultrasonographically guided aspiration.

OBJECTIVE

To determine the impact of ultrasonography on the diagnostic accuracy of fine needle aspiration cytology (FNAC) of the thyroid.

STUDY DESIGN

We compared two FNAC series. In period 1 we used neither ultrasonograph nor ultrasonographically-guided FNAC in the evaluation of thyroid nodules, while both tools were routinely applied in period 2. Moreover, in the former period all cellular follicular lesions were encountered among suspicious findings, while in period 2 we advised regular follow-up examinations instead of immediate surgery for patients with no significant atypia. The basis of follow-up examinations was ultrasonographic volumetry of the nodule and repeat FNAC on growing nodules.

RESULTS

The number of FNAC, positive predictive value of FNAC, number of malignancies, sensitivity, the specificity and diagnostic accuracy were higher in period 2 as compared with period 1: 3,446 vs. 1,448; 45% vs. 16%, 39 vs. 29, 92% vs. 76%, 65% vs. 87% and 66% vs. 87%, respectively.

CONCLUSION

The introduction of ultrasonography permits higher diagnostic accuracy of the evaluation process. This is achieved not only by lessening false negative reports but, more important, by decreasing false positive results.