Ultrasound guided cytology is performed in close to a 100% of patients with thyroid nodules at Sahlgrenska University Hospital (SUH). In 2017 the EU-TIRADS was introduced at SUH in 2019 in an organised and wide scale. This retrospective single centre study enlightens factors contributing to increase accuracy within the diagnostic field of pre-operative thyroid cytology.

The Swedish Information Network for Cancer Care (INCA) provided data from 2013 to 2022 with preoperative diagnosis of papillary cancer. The national cohort was subdivided in regional (Västra Götaland region) and patients at SUH. Patients were stratified by before and after onset of the introduction of the EU-TIRADS. Group 1 was defined as 1st of January 2013 to 31st of December 2018, and group 2 subsequently after 1st of January 2019 to 31st of December 2022.

Group 1 had a post-operative diagnosis concurring with pre-operative cytology in 47% of the cases in comparison with group 2 with 70,5 % in Västra Götaland region. Patients from SUH separately analysed, displayed 44% correct pre-operative diagnosis in group 1 compared to 77% in group 2. National cohort displayed 45,2% in group 1 and 61,2% in group 2. The increase of correct pre-operative cytology in group was also congruent with a timeline of staff shift at SUH.

This single centre retrospective study shows that the introduction of the TIRADS-system improved the accuracy of cytology in comparison to post-operative diagnosis. We also suggest that having several cytologists may improve outcome due to the difficult and subjective nature of the Bethesda classification.