Question How has reported thyroid nodule size changed over time?
Findings In this systematic review and meta-analysis of 28 studies and 11 963 patients, reported thyroid nodule size increased during the last 30 years in diagnostic ultrasonography studies while reported nodule size decreased in screened populations.
Meaning The study results suggest that the size of thyroid nodules reported on thyroid ultrasonography has increased over time concomitant with changing nodule risk stratification systems and guidelines that have been designed to improve diagnostic yield and reduce overdetection of subclinical disease.
Importance In recent years, concern has grown around the overdetection of thyroid cancer. Changes to thyroid nodule risk stratification systems and guidelines were made to improve diagnostic yield. It is not known how these advancements have affected the size of thyroid nodules reported on ultrasonography over time.
Objective To evaluate change in reported nodule size since 1990, particularly between studies of thyroid ultrasonography obtained for diagnostic vs screening purposes.
Study Selection The systematic review included original research studies that reported thyroid nodule size in adults undergoing their first thyroid ultrasonography. Excluded studies were those that included patients with known thyroid disease, prior thyroid ultrasonography, nodules identified through other imaging modalities, and/or that had constraints on nodule size and/or characteristics.
Data Sources PubMed, SCOPUS, CENTRAL, and CINAHL were reviewed from January 1990 to March 2021. Study characteristics, patient demographic characteristics, nodule size, and ultrasonography techniques were independently extracted by multiple observers.
Main Outcomes and Measures The size of thyroid nodules reported via ultrasonography over time. Mixed-effects meta-regression models were used to evaluate mean nodule size (1) overall, (2) in studies that used ultrasonography diagnostically, and (3) in studies that used ultrasonography for screening.
Results A total of 11 963 patients were included; the mean (SD) age was 47.6 (5.2) years. A total of 1097 studies were identified; of these, 395 full-text articles were assessed, and 18 studies met inclusion criteria. All were done at academic institutions. Altogether, these studies had 11 963 patients who underwent a first thyroid ultrasonography. Reported mean nodule size increased 0.52 mm each year from 1990 to 2021 (95% CI, 0.2-0.81). Diagnostic subgroup mean nodule size increased 0.57 mm each year from 1990 to 2021 (95% CI, 0.21-0.93). Screening subgroup mean nodule size decreased by 0.23 mm each year up to 2012 (95% CI, -0.40 to -0.07).