Carlé Allan, Laurberg Peter, Pedersen Inge Bülow, Knudsen Nils, Perrild Hans, Ovesen Lars, Rasmussen Lone Banke, Jørgensen Torben
Department of Endocrinology and Medicine, Aalborg Hospital, Aarhus University Hospital, Denmark.
J Clin Epidemiol. 2009 Apr;62(4):446-51. doi: 10.1016/j.jclinepi.2008.06.016. Epub 2008 Oct 21.
Studies of hypothyroidism are often based on patients referred to hospital. It is unknown, to what extent such studies are referral biased. Thus, the aim of the present study was to evaluate the magnitude of selection bias in a study of patients newly diagnosed with hypothyroidism.
A computer-based system linked to laboratory databases identified patients with incident overt hypothyroidism (n=346) from 1997 to 2000 in Aalborg, Denmark. An electronic patient administrative system identified patients referred to Department of Endocrinology, Aalborg Hospital. Among patient characteristics recorded at the time of diagnosis-age, gender, nosological subgroup of hypothyroidism, thyroid stimulating hormone (TSH), total thyroxine (T4), total triiodothyronine (T3), thyroid peroxidase antibody (TPOAb), thyroglobulin antibody (TgAb), and calendar year--we searched for predictors of referral state.
Of all hypothyroid patients, 86 (25%) were referred to our endocrine unit. The referred patients were younger (50.4 vs. 66.0 years, P<0.001), had higher serum TSH (53.6 vs. 32.6 mU/L, P=0.002) and lower serum total T4 (37.0 vs. 44.0 nmol/L, P=0.03) compared with nonreferred patients. In a multivariate model, only less age (P<0.001) and serum total T4 (P=0.03) were statistically associated with referral state.
Hypothyroid patients referred to a specialized hospital unit were younger and marginally more hypothyroid than nonreferred patients. Thus, referral bias should always be considered in hospital-based studies of hypothyroid patients.
甲状腺功能减退症的研究通常基于转诊至医院的患者。目前尚不清楚此类研究在多大程度上存在转诊偏倚。因此，本研究的目的是评估一项针对新诊断甲状腺功能减退症患者的研究中选择偏倚的程度。
一个与实验室数据库相连的计算机系统识别出了1997年至2000年丹麦奥尔堡新发生明显甲状腺功能减退症的患者（n = 346）。一个电子患者管理系统识别出转诊至奥尔堡医院内分泌科的患者。在诊断时记录的患者特征（年龄、性别、甲状腺功能减退症的疾病亚组、促甲状腺激素（TSH）、总甲状腺素（T4）、总三碘甲状腺原氨酸（T3）、甲状腺过氧化物酶抗体（TPOAb）、甲状腺球蛋白抗体（TgAb）和日历年份）中，我们寻找转诊状态的预测因素。
在所有甲状腺功能减退症患者中，86例（25%）被转诊至我们的内分泌科。与未转诊患者相比，转诊患者更年轻（50.4岁对66.0岁，P < 0.001），血清TSH更高（53.6对32.6 mU/L，P = 0.002），血清总T4更低（37.0对44.0 nmol/L，P = 0.03）。在多变量模型中，只有年龄较小（P < 0.001）和血清总T4（P = 0.03）与转诊状态存在统计学关联。
转诊至专科医院的甲状腺功能减退症患者比未转诊患者更年轻，甲状腺功能减退程度略高。因此，在基于医院的甲状腺功能减退症患者研究中应始终考虑转诊偏倚。
