Reducing the Number of Unnecessary Thyroid Biopsies While Improving Diagnostic Accuracy

Toward the 'Right' TIRADS

Giorgio Grani; Livia Lamartina; Valeria Ascoli; Daniela Bosco; Marco Biffoni; Laura Giacomelli; Marianna Maranghi; Rosa Falcone; Valeria Ramundo; Vito Cantisani; Sebastiano Filetti; Cosimo Durante


J Clin Endocrinol Metab. 2019;104(1):95-102. 

In This Article

Abstract and Introduction


Context: The prevalence of thyroid nodules in the general population is increasingly high, and at least half of those biopsied prove to be benign. Sonographic risk-stratification systems are being proposed as "rule-out" tests that can identify nodules that do not require fine-needle aspiration (FNA) cytology.

Objective: To comparatively assess the performances of five internationally endorsed sonographic classification systems [those of the American Thyroid Association, the American Association of Clinical Endocrinologists, the American College of Radiology (ACR), the European Thyroid Association, and the Korean Society of Thyroid Radiology] in identifying nodules whose FNAs can be safely deferred and to estimate their negative predictive values (NPVs).

Design: Prospective study of thyroid nodules referred for FNA.

Setting: Single academic referral center.

Patients: Four hundred seventy-seven patients (358 females, 75.2%); mean (SD) age, 55.9 (13.9) years.

Main Outcome Measures: Number of biopsies classified as unnecessary, false-negative rate (FNR), sensitivity, specificity, predictive values, and diagnostic ORs for each system.

Results: Application of the systems' FNA criteria would have reduced the number of biopsies performed by 17.1% to 53.4%. The ACR Thyroid Imaging Reporting and Data System (TIRADS) allowed the largest reduction (268 of 502) with the lowest FNR (NPV, 97.8%; 95% CI, 95.2% to 99.2%). Except for the Korean Society of Thyroid Radiology TIRADS, all other systems exhibited significant discriminatory performance but produced significantly smaller reductions in the number of procedures.

Conclusions: Internationally endorsed sonographic risk stratification systems vary widely in their ability to reduce the number of unnecessary thyroid nodule FNAs. The ACR TIRADS outperformed the others, classifying more than half the biopsies as unnecessary with a FNR of 2.2%.


The number of individuals harboring sonographically detected thyroid nodules continues to rise, with an estimated 219 million in the United States alone. The challenge for clinicians is to identify those rare nodules harboring a clinically relevant malignancy.[1] Fine-needle aspiration (FNA) has traditionally been used for this purpose.[2–4] However, at least half of all biopsied nodules prove to be benign,[5] and up to one third have cytological findings that are inconclusive.[6] Strategies for the clinical management of thyroid nodule patients have therefore evolved:[6] ultrasonography now plays a larger role,[1] informing decisions on the need for FNA[7,8] and plans for long-term follow-up.[7,8] To improve the accuracy of this guidance, ultrasound-based risk-stratification systems have now been developed by many national and international thyroid societies[7–10] and by the American College of Radiology (ACR).[11]

Robust evidence is lacking on the relative strengths and weaknesses of the various systems. Some systems have been validated in multicenter studies.[12,13] Independent validation and comparison studies (generally involving two to three of the systems) have mostly been retrospective.[14–19] In a recent study involving central re-evaluation of nodules in a multi-institutional database, the 2017 ACR Thyroid Imaging Reporting and Data System (TIRADS) was found to compare favorably with the American Thyroid Association (ATA) guidelines and the Korean Society of Thyroid Radiology TIRADS (K-TIRADS), primarily because it more effectively reduced the number of biopsies performed on benign nodules.[20] The largest prospective study of this type[21] compared the systems developed by the British Thyroid Association, the ATA, and the American Association of Clinical Endocrinologists (AACE)/American College of Endocrinology (ACE)/Associazione Medici Endocrinologi (AME) and found no significant differences between their overall diagnostic accuracy parameters.

To obtain a broader picture of the merits and demerits of currently available sonographic risk-stratification systems, we conducted a prospective, observational study of 502 thyroid nodules referred to our center for FNA. During the real-time pre-FNA ultrasound examinations, each nodule was classified using five internationally endorsed systems, and the recommendation for FNA was analyzed in light of the nodule's pathologic diagnosis. Because a major aim of all of these systems is to eliminate unnecessary thyroid biopsies without jeopardizing the detection of clinically significant malignancies, our aims were to determine[1] the proportion of nodules whose biopsy would have been considered unnecessary by each system, and[2] the reliability of these exclusions, as reflected by multiple parameters of diagnostic accuracy.