Modified Bethesda criteria for thyroid aspirates significantly decrease nondiagnostic rates without decreasing...

Area of Science:

• Cytopathology
• Thyroid Fine Needle Aspiration (FNA)
• Diagnostic Accuracy

Background:

• Thyroid nodule evaluation relies on fine needle aspiration (FNA) cytology.
• The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) defines adequacy criteria.
• Previous studies suggest modifying TBSRTC adequacy criteria can improve aspirate adequacy rates.

Purpose of the Study:

• To prospectively evaluate the performance of modified Bethesda System adequacy criteria.
• To assess the impact of altered criteria on nondiagnostic rates and diagnostic accuracy.
• To determine if modifications affect the sensitivity of subsequent molecular testing.

Main Methods:

• A 6-year prospective study classifying thyroid aspirates with 1-59 follicular cells as "nondiagnostic, favor benign" or "scant but adequate".
• Scant but adequate cases were categorized as benign (Bethesda category 2) or atypia of undetermined significance (AUS) (Bethesda category 3).
• Bethesda category 3 cases underwent Afirma molecular testing.

Main Results:

• Modified criteria reduced the overall nondiagnostic rate from 22% to 10% (P <0.001).
• The rate of "nondiagnostic, favor benign" was 3%, with a 2.6% risk of malignancy upon follow-up.
• The rate of "scant but adequate" and benign was 8% (0% risk of malignancy), and "scant but adequate" with AUS was 4% (18% suspicious rate, 50% risk of malignancy).
• No significant difference in the "suspicious" rate or risk of malignancy was observed compared to standard adequate cases.

Conclusions:

• Modified Bethesda adequacy criteria effectively decrease nondiagnostic rates in thyroid aspirates.
• These modifications do not compromise the diagnostic sensitivity for malignancy.
• Altered criteria offer a valuable approach to improve thyroid FNA sample adequacy.