LAUSR

Objectives This study aims to evaluate whether the use of thyroid ultrasound (US) early in the work-up of suspected thyroid disorders triggers cascade effects of medical procedures and to analyse effects on morbidity, healthcare usage and costs. Study design Retrospective analysis of claims data from ambulatory care (2012–2017). Setting Primary care in Bavaria, Germany, 13 million inhabitants. Participants Patients having received a thyroid stimulating hormone (TSH) test were allocated to (1) observation group: TSH test followed by an early US within 28 days or (2) control group: TSH test, but no early US. Propensity score matching was used adjusting for socio-demographic characteristics, morbidity and symptom diagnosis (N=41 065 per group after matching). Primary and secondary outcome measures Using cluster analysis, groups were identified regarding frequency of follow-up TSH tests and/or US and compared. Results Four subgroups were identified: cluster 1: 22.8% of patients, mean (M)=1.6 TSH tests; cluster 2: 16.6% of patients, M=4.7 TSH tests; cluster 3: 54.4% of patients, M=3.3 TSH tests, 1.8 US; cluster 4: 6.2% of patients, M=10.9 TSH tests, 3.9 US. Overall, reasons that explain the tests could rarely be found. An early US was mostly found in clusters 3 and 4 (83.2% and 76.1%, respectively, were part of the observation group). In cluster 4 there were more women, thyroid-specific morbidity and costs were higher and the early US was more likely to be performed by specialists in nuclear medicine or radiologists. Conclusion Presumably unnecessary tests in the field of suspected thyroid diseases seem to be frequent, contributing to cascades effects. Neither German nor international guidelines provide clear recommendations for or against US screening. Therefore, guidelines on when to apply US and when not are urgently needed.