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Comment & Response
June 2014

Clinical Decision Making in Patients With Thyroid Nodules—Reply

Author Affiliations
  • 1Department of Radiology and Biomedical Imaging, University of California, San Francisco
  • 2Department of Epidemiology and Biostatistics, University of California, San Francisco
  • 3Department of Health Policy and Obstetrics, Gynecology and Reproductive Sciences, University of California, San Francisco
  • 4Radiology Outcomes Research Lab, University of California, San Francisco
JAMA Intern Med. 2014;174(6):1006. doi:10.1001/jamainternmed.2014.38

In Reply My colleagues and I thank Gross and colleagues for giving us the opportunity to clarify our study.1 To determine whether a nodule was benign or malignant, we included the results of all biopsies conducted at the University of California, San Francisco, and linked the entire cohort of more than 8000 patients with the California Cancer Registry (CCR) that collects cancer incidence data on all patients who received a diagnosis in California and 22 additional states with whom the CCR shares data. By linking with the CCR, we learned about cancers that occurred as long as 6 years after ultrasonography and confirmed that nodules were benign as long as 11 years after ultrasonography. Thus, we know with a high degree of certainty which nodules were malignant or benign. In contrast, all previous of thyroid ultrasonography studies limited their analysis to patients who underwent immediate biopsy, where the decision to perform a biopsy was influenced by the ultrasonography result. This will miss cancers that would not have been considered suspicious on the ultrasonogram, and this ascertainment bias will overestimate the accuracy of ultrasonography. This is why we found a lower risk of cancer and lower predictive values associated with specific findings compared with prior reports: this reflects our complete follow-up of patients many years after ultrasonography to determine the true cancer status in the entire cohort. The completeness of cancer information makes our cohort the most representative and accurate way to estimate the risk of cancer among patients in whom incidental thyroid nodules are identified.

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