尚未描述 2020 年至 2021 年大流行期间，COVID-19 变体的出现如何影响甲状腺癌诊断率。估计前 2 年期间按组织学类型划分的甲状腺癌未确诊病例总数通过将观察到的发病率与预期发病率进行比较，并测试同期发病时癌症大小与前几年相比的变化，对 COVID-19 大流行的年份（2020 年和 2021 年）进行了分析。这项纵向研究分析了 2016 年至 2016 年甲状腺癌诊断的趋势2021 年美国成年人使用来自监测、流行病学和最终结果 22 (SEER-22) 计划数据库的数据。数据分析于 2024 年 4 月至 5 月进行。每 100000 名美国成年人的年龄调整发病率、发病率变化、估计未确诊病例数和平均癌症大小。2016 年第一季度和2019 年分别为每 10 万人 21.0 和 18.8。 2020 年至 2021 年，季度比率分别为每 10 万人 17.3、11.1、17.2、17.9、17.4、19.0、17.1 和 17.3。观察到的2厘米或更小的乳头状癌的甲状腺癌发病率降低了11%（风险比[RR]，0.89；95% CI，0.83-0.95），大于2厘米的乳头状癌的甲状腺癌发病率降低了14%（RR，0.86；95） % CI，0.79-0.93），滤泡癌为 8%（RR，0.92；95% CI，0.82-0.92），髓样癌为 10%（RR，0.90；95% CI，0.78-1.04），髓样癌为 15% 2020 年 3 月至 2021 年 12 月间变性癌症（RR，0.85；95% CI，0.68-1.07）。嗜酸细胞癌的发病率在大流行初期有所下降，但到 2021 年，发病率恢复到基线或以上（RR，1.15；95% CI， 0.97-1.37）。外推到美国普通人群，从 2020 年 3 月到 2021 年 12 月，未诊断的甲状腺癌病例总数（预期减去观察到）约为 10200 例：5400 例 2 厘米或更小的乳头状癌（95% CI，2380-8530）， 3700 例大于 2 cm 的乳头状癌（95% CI，1660-5810）、600 例滤泡状癌（95% CI，-260 至 1550）、300 例髓样癌（95% CI，-110 至 720）和 190 例间变性癌（ 95% CI，-75 至 530）。 2016 年至 2021 年间，任何组织学类型的诊断时平均大小没有显着变化。这项纵向研究发现，到 2021 年底，许多甲状腺癌仍未确诊。这些癌主要是小乳头状癌，但也影响除嗜酸细胞癌以外的所有组织学类型。这些诊断缺陷可能会导致未来患有更大或更晚期癌症的患者比例暂时增加，从而导致人口发病率和死亡率暂时增加。

How rates of thyroid cancer diagnosis were affected by the emergence of COVID-19 variants during the 2020 to 2021 era of the pandemic has not been described.To estimate the total number of undiagnosed cases of thyroid cancer, by histologic type, during the first 2 years of the COVID-19 pandemic (2020 and 2021) by comparing observed to expected incidence and to test for changes in size of cancer at incidence during the same period compared to prior years.This longitudinal study analyzed trends in thyroid cancer diagnoses from 2016 to 2021 among US adults using data from the Surveillance, Epidemiology, and End Results 22 (SEER-22) program database. Data analyses were performed in April to May 2024.Age-adjusted incidence rate per 100 000 US adults, changes in incidence, estimated number of undiagnosed cases, and mean cancer size.Absolute rates of overall thyroid cancer incidence in the first quarter of 2016 and of 2019 were 21.0 and 18.8 per 100 000, respectively. From 2020 through 2021, the quarterly rates were 17.3, 11.1, 17.2, 17.9, 17.4, 19.0, 17.1, and 17.3 per 100 000, respectively. The observed incidence of thyroid cancers decreased by 11% for papillary cancers 2 cm or smaller (risk ratio [RR], 0.89; 95% CI, 0.83-0.95), 14% for papillary cancers larger than 2 cm (RR, 0.86; 95% CI, 0.79-0.93), 8% for follicular cancers (RR, 0.92; 95% CI, 0.82-0.92), 10% for medullary cancers (RR, 0.90; 95% CI, 0.78-1.04), and 15% for anaplastic cancers (RR, 0.85; 95% CI, 0.68-1.07) from March 2020 to December 2021. Oncocytic cancers declined in incidence early in the pandemic, but rates returned to baseline or above through 2021 (RR, 1.15; 95% CI, 0.97-1.37). Extrapolated to the general US population, the total estimated number of thyroid cancer cases not diagnosed (expected minus observed) from March 2020 to December 2021 was approximately 10 200: 5400 papillary cancers 2 cm or smaller (95% CI, 2380-8530), 3700 papillary cancers larger than 2 cm (95% CI, 1660-5810), 600 follicular cancers (95% CI, -260 to 1550), 300 medullary cancers (95% CI, -110 to 720), and 190 anaplastic cancers (95% CI, -75 to 530). Mean size at diagnosis did not change significantly between 2016 and 2021 for any histologic type.This longitudinal study found that by the end of 2021, many thyroid cancers remained undiagnosed. These were predominantly small papillary cancers but also affected all histologic types except oncocytic. These deficits in diagnosis could produce a temporary increase in the rate of patients presenting with larger or more advanced stage cancers in the future, and consequently, temporary increases in population morbidity and mortality.