背景:不同实验室的甲状腺检测策略各不相同。一线联合促甲状腺激素(TSH)和freeT4(FT4)历来受到许多实验室的青睐,因为这可以检测出未经诊断的中枢甲状腺功能减退症患者,而一线仅TSH策略可能会错过。然而,缺乏对这种方法的效用的最新评估。
目的:我们在目前的实践中研究了一线TSH和FT4在检测中枢甲状腺功能减退症中的临床应用。
■查询全威尔士实验室信息系统,以识别年龄≥16岁的FT4降低和TSH不适当(低FT4)患者的甲状腺功能检查。使用年中人口数据确定低FT4的1年发病率。回顾了低FT4患者的临床信息,以确定低FT4的原因和中枢甲状腺功能减退症的发生率。
结果:低FT4的发生率根据FT4测定方法而变化(范围:98-301例/100,000人口/年)。在两个卫生委员会中发现了15例新的中央甲状腺功能减退症病例,相当于2例/10万人口/年。低FT4对中心性甲状腺功能减退症的阳性预测值为2%-4%。在初级保健患者的横截面中,在所有甲状腺检查中,有0.5%检测到低FT4,检测率与试验相关差异.
结论:尽管低FT4是一个常见的实验室发现,中心性甲状腺功能减退症的发病率仍然罕见.随着目前甲状腺检测率的增加和减少FT4的药物使用的增加,低FT4对中枢甲状腺功能减退症的预测价值比以前报道的要低得多。甲状腺筛查策略将需要平衡来自一线TSH和FT4测试的产量与调查具有非病理学实验室异常的个体的成本。
BACKGROUND: Thyroid testing strategies vary across laboratories. First-line combined thyroid stimulating hormone (TSH) and freeT4 (FT4) have historically been preferred by many laboratories as this detects individuals with undiagnosed central hypothyroidism who can be missed with a first-line TSH-only strategy. However, an up-to-date evaluation of the utility of this approach is lacking.
OBJECTIVE: We investigated the clinical utility of first-line TSH and FT4 in the detection of central hypothyroidism in current day practice.
UNASSIGNED: The All-Wales laboratory information system was queried to identify thyroid function tests in patients aged ≥16 years with decreased FT4 and inappropriate TSH (low-FT4). The 1-year incidence of low-FT4 was determined using mid-year population data. Clinical information of patients with low-FT4 was reviewed to determine causes of low-FT4 and the incidence of central hypothyroidism.
RESULTS: The incidence of low-FT4 varied according to FT4 assay method (range: 98-301 cases/100,000 population/year). Fifteen new cases of central hypothyroidism were detected in two health boards, equivalent to 2 cases/100,000 population/year. Positive predictive value of low-FT4 for central hypothyroidism was 2%-4%. In a cross-section of primary care patients, low-FT4 was detected in 0.5% of all thyroid tests with assay-related differences in detection rates.
CONCLUSIONS: Although low-FT4 is a common laboratory finding, the incidence of central hypothyroidism remains rare. With the currently increased rates of thyroid testing and increased use of medications that decrease FT4, low-FT4 has a much lower predictive value for central hypothyroidism than previously reported. Thyroid screening strategies will need to balance the yield from first line TSH and FT4 testing with the cost of investigating individuals with non-pathological laboratory abnormalities.