Developing a Registry for Thyroid Incidentalomas: Lessons Learned and the Path Forward.

Background: Incidentalomas are findings on an imaging test done for other reasons, for which there are no matching symptoms in the patient. They are common in the adrenal gland, pancreas, liver, and thyroid, among other sites. Incidentalomas are a problem because we have a limited understanding of their natural history: it is difficult to know how much of a threat they pose to individual patients. An observational registry that would allow a systematic study of thyroid incidentalomas could reveal their natural history and the effect of detection on patients' lives, as well as document the cost to the healthcare system. A registry would help to determine which incidentalomas could be monitored and which require action.

Study Design: A cohort study was conducted, with case identification via radiology imaging reports with follow-up through a minimum of one year post-identification.

Results: In one year, >109,000 imaging studies were performed that might reveal an incidental thyroid finding (computed tomography scans of the neck or chest, magnetic resonance imaging of the neck, plain x-ray of the chest, non-thyroid directed ultrasound of the neck, positron emission tomography scan, or myocardial perfusion scan). A total of 125 patients were identified as having a thyroid nodule, with a <1% reporting rate among eligible imaging studies, much lower than other published estimates of incidental thyroid nodule prevalence on imaging. Of the 125 nodules, 46 had been previously identified (were not "new"). Of the 79 patients with new nodules, more than half (44; 53%) were not notified of the finding. The approved study design allowed contact only with those who had been clearly notified of their thyroid nodule. Among those who could be reached, many did not recall the finding (6/15; 40%). Of those who did recall the finding, none self-identified it as an incidentaloma.

Conclusions: There are serious logistical and ethical hurdles to developing observational registries of incidentalomas, as well as threats to data validity because incidentalomas are incompletely identified, reported, and acted upon. Solutions commonly used to optimize data quality for registries would increase reporting, but could potentially overwhelm the healthcare system and harm patients. A novel interventional design that is proposed here for future work may facilitate both study and amelioration of the problem.