Choosing the best algorithm among five thyroid nodule ultrasound scores: from performance to cytology sparing-a single-center retrospective study in a large cohort

Abstract

Objective: Incidental diagnosis of thyroid nodules, and therefore of thyroid cancer, has definitely increased in recent years, but the mortality rate for thyroid malignancies remains very low. Within this landscape of overdiagnosis, several nodule ultrasound scores (NUS) have been proposed to reduce unnecessary diagnostic procedures. Our aim was to verify the suitability of five main NUS.

Methods: This single-center, retrospective, observational study analyzed a total number of 6474 valid cytologies. A full clinical and US description of the thyroid gland and nodules was performed. We retrospectively applied five available NUS: KTIRADS, ATA, AACE/ACE-AME, EUTIRADS, and ACRTIRADS. Thereafter, we calculated the sensitivity, specificity, PPV, and NPV, along with the number of possible fine-needle aspiration (FNA) sparing, according to each NUS algorithm and to clustering risk classes within three macro-groups (low, intermediate, and high risk).

Results: In a real-life setting of thyroid nodule management, available NUS scoring systems show good accuracy at ROC analysis (AUC up to 0.647) and higher NPV (up to 96%). The ability in FNA sparing ranges from 10 to 38% and reaches 44.2% of potential FNA economization in the low-risk macro-group. Considering our cohort, ACRTIRADS and AACE/ACE-AME scores provide the best compromise in terms of accuracy and spared cytology.

Conclusions: Despite several limitations, available NUS do appear to assist physicians in clinical practice. In the context of a common disease, such as thyroid nodules, higher accuracy and NPV are desirable NUS features. Further improvements in NUS sensitivity and specificity are attainable future goals to optimize nodule management.

Key points: • Thyroid nodule ultrasound scores do assist clinicians in real practice. • Ultrasound scores reduce unnecessary diagnostic procedures, containing indolent thyroid microcarcinoma overdiagnosis. • The variable malignancy risk of the "indeterminate" category negatively influences score's performance in real-life management of thyroid lesions.

Keywords: Biopsy, fine-needle; Cytology sparing; Thyroid imaging, reporting, and data system; Thyroid nodules; Ultrasonography.

Fig. 1

Flowchart of the study. ^aExcluded for incomplete data or inconclusive cytology or sub-centimetric size (fine-needle aspiration is rarely indicated by any TIRADS for the latter). ^bIndeterminate cytology: of those, 283 were classified as Thy3, according to the British Cytological classification (before 2014), and, later on, 596 ones as TIR3A (370) and TIR3B (226), according to the SIAPEC-IAP classification. Ø = size of the lesion

Fig. 2

a ROC curves according to positive cytology for all NUS scores. The area under ROC curves are 0.623 (CI 95%; 0.599–0.647) for KTIRADS; 0.632 (CI 95%; range 0.608–0.656) for ATA; 0.623 (CI 95%; 0.599–0.646) for AACE/ACE-AME; 0.606 (CI 95%; 0.582–0.631) for EUTIRADS; 0.622 (CI 95%; 0.600–0.645) for ACRTIRADS range 1–5. b ROC curve considering the total scoring of ACRTIRADS (points 1–14). The area under ROC curve is 0.647 (CI 95%; 0.625–0.669)