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.