Ultrasound grading of thyroid nodules using the BTA U-scoring guidelines - Is there evidence of intra-and interobserver variability?

Comparison of British Thyroid Association and TIRADS classifications and their impact on the radiological and surgical management of indeterminate thyroid nodules

AIM

The British Thyroid Association (BTA) Guidelines for the Management of Thyroid Cancer advocate for fine-needle aspiration cytology for all thyroid nodules graded indeterminate (U3) at ultrasound assessment. This approach raises concerns regarding potential over-diagnosis of low-risk lesions. Conversely, equivalent Thyroid Imaging Reporting and Data Systems (TIRADS) guidelines permit surveillance or discharge of indeterminate thyroid nodules of certain sizes. This service analysis analyses how guideline choice impacts the fine-needle aspiration cytology rate and subsequent surgical management of indeterminate thyroid nodules.

MATERIALS AND METHODS

All patients with an indeterminate (U3) thyroid nodule identified on ultrasound over a 12-month period were included. Indeterminate thyroid nodules were retrospectively rescored using three equivalent TIRADS classifications by three independent reviewers, blinded to the histopathology. Hypothetical differences in fine-needle aspiration cytology rates and surgical activity were then compared.

RESULTS

Ninety-six nodules were identified. Retrospective application of TIRADS guidelines resulted in a hypothetical 44.8-55.2% reduction in fine-needle aspiration cytology performed for indeterminate thyroid nodules compared to BTA. A statistically significant increase in rates of surgical activity for indeterminate thyroid nodules was observed between BTA guidance and all retrospectively applied TIRADS guidelines (p < 0.001). Of four confirmed thyroid cancers, three would have been unanimously removed.

CONCLUSION

Under BTA guidance, increased fine-needle aspiration cytology rates for indeterminate thyroid nodules resulted in significantly increased surgical activity in our cohort compared to retrospectively applied TIRADS guidelines.

Evaluation of the departmental inter-rater reliability when scoring thyroid nodules according to the British Thyroid Association Ultrasound-classification model: Is there significant disagreement?

Introduction

The British Thyroid Association Ultrasound-classification is a risk stratification model which grades thyroid nodules in U2-5 based on their sonographic appearance. Existence of variability between the ultrasound operators when U-scoring is reported in the literature with some evidence found in the author's department. The aim of this study was to investigate whether there is significant disagreement in the department and identify potential reasons for variability.

Methods

Eight operators, radiologists and sonographers, were recruited to grade 33 TNs and answer a tick box questionnaire using the British Thyroid Association lexicon. The inter-operator variability for the U-categories, indication for fine-needle aspiration biopsy and ultrasound features was assessed using Fleiss' kappa and Gwet-AC1. The operators' accuracy was measured against the most experienced operator in the department using Cohen's kappa and percentage agreement.

Results

Fair agreement (Fleiss' K = 0.21) was obtained between the participants when U-scoring (U2-5). Fair-to-moderate agreement was noted between sonographers (K = 0.40). Significant variability was demonstrated between radiologists (p > 0.05). Indication for fine-needle aspiration biopsy reached fair to almost substantial agreement (radiologists' AC1 = 0.34, sonographers' AC1 = 0.58, overall AC1 = 0.41). No significant variability measured for echogenicity (K = 0.29), composition (K = 0.33), shape (K = 0.58), margin (K = 0.45), halo (K = 0.34) and vascularity (K = 0.44). Accuracy reached fair agreement (mean Cohen's K = 0.29) and moderate agreement (mean AC1 = 0.53) for the U-categories and fine-needle aspiration biopsy, respectively. Radiologists demonstrated lower accuracy.

Conclusion

No significant inter-rater variability in U-scoring or recommending fine-needle aspiration biopsy was demonstrated between all the operators in the department. Radiologists showed significant variability in U-scoring and lower accuracy. Reliability and accuracy could be improved by addressing those problematic categories and features identified with this study.

Ultrasound for the assessment of thyroid nodules: an overview for non-radiologists

Upon discovery of a thyroid nodule (or nodules), a patient is usually referred for evaluation by ultrasound, which is typically performed by a trained radiologist or sonographer. More recently, this technology has been used intraoperatively by endocrine surgeons and also by endocrinologists, often in the context of ‘one-stop shops’ or point of care ultrasound in the outpatient setting. Although thyroid nodules are common and most will be benign, the subsequent work up of these can cause anxiety for patients and place a burden on radiologists. In the UK, sonographic features of benign, suspicious or malignant nodules are classified by the British Thyroid Association U1–U5 criteria, which decide whether to biopsy the nodule (typically U3 and above). This article provides an overview of ultrasound in assessing the thyroid nodule in the context of this classification. This can be used as a guide to interpretation of thyroid ultrasonography for non-radiologists.