Inappropriate use of thyroid ultrasound: a systematic review and meta-analysis

Purpose: Nearly half the cases of thyroid cancer, a malignancy rapidly rising in incidence within the United States, are attributable to small and asymptomatic papillary thyroid cancers that will not increase mortality. A primary driver of thyroid cancer overdiagnosis is ultrasound use. It is therefore valuable to understand how inappropriate use of thyroid ultrasound is defined, analyze the current evidence for its frequency, and identify interventions to lessen misuse. Methods: Ovid MEDLINE(R), Ovid EMBASE, and Scopus databases were searched from inception to June 2020 for studies assessing inappropriate use of thyroid ultrasound. Reviewers, working independently and in duplicate, evaluated studies for inclusion, extracted data, and graded risk of bias. We used a random-effects model with a generalized linear mixed approach to calculate the mean overall proportion estimates of inappropriate use. Results: Seven studies (total n = 1573) met the inclusion criteria with moderate to high risk of bias. Inappropriate thyroid ultrasound use was described variably, using published practice guidelines, third-party expert reviewers, or author interpretations of the literature. The overall frequency of inappropriate thyroid ultrasound use was 46% (95% CI 15–82%; n = 388) and 34% (95% CI 16–57%; n = 190) among studies using guideline based definitions. The pooled frequency of iUS due to thyroid dysfunction (either hypothyroidism or thyrotoxicosis) was 17% (95% CI 7–37%; n = 191) and the frequency of iUS due to nonspecific symptoms without a palpable mass was 11% (95% CI 5–22%; n = 124). No study examined interventions to address inappropriate use. Conclusions: Low quality evidence suggests that inappropriate use of thyroid ultrasound is common. Interventional studies aiming to decrease the inappropriate use of thyroid ultrasound are urgently needed.