Physician's Prescribing Preference as an Instrumental Variable Exploring Assumptions Using Survey Data
Physician's Prescribing Preference as an Instrumental Variable Exploring Assumptions Using Survey Data
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DOI：
10.1097/ede.0000000000000425
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发表时间：
2016-03-01
期刊：
影响因子：
5.4
通讯作者：
den Elzen, Wendy P. J.
中科院分区：
文献类型：
--
作者：
Boef, Anna G. C.;le Cessie, Saskia;den Elzen, Wendy P. J.
背景：医生的处方偏好越来越多地被用作治疗效果研究的工具变量。然而，医生之间处方模式的差异可能反映了偏好或病例组合的差异。方法：对荷兰、英国、新西兰、爱尔兰、瑞士和德国的全科医生(GP)进行了一项调查，询问他们是否会给8名虚构的亚临床甲状腺功能减退症患者开左旋甲状腺素。我们调查了(1)医生偏好的变化是否可观察到，以及全科医生及其患者群体的特征在多大程度上解释了这种变化，以及(2)数据是否符合确定性和随机单调性假设。结果：在526名回答的全科医生中，左旋甲状腺素处方有很大差异。在初始混合效应Logistic模型中，左甲状腺素处方(Logit量表)的Gp间方差为9.9(95%可信区间：8.0，12)，添加固定效应后为8.3(6.7，10)，添加GP特征后为8.2(6.6，10)。出现的处方模式证伪了确定性的单调性假设。如果同一GP的不同病例接受左旋甲状腺素治疗，所有国家的所有病例都更有可能接受左旋甲状腺素治疗，这与随机单调性假设相一致。结论：我们的研究支持医生偏好作为治疗决策的决定因素的存在。确定性的单调性对于医生作为一种工具的偏好通常是不可信的。根据工具的定义，随机单调性可能是合理的。
Background: Physician's prescribing preference is increasingly used as an instrumental variable in studies of therapeutic effects. However, differences in prescribing patterns among physicians may reflect differences in preferences or in case-mix. Furthermore, there is debate regarding the possible assumptions for point estimation using physician's preference as an instrument.Methods: A survey was sent to general practitioners (GPs) in The Netherlands, the United Kingdom, New Zealand, Ireland, Switzerland, and Germany, asking whether they would prescribe levothyroxine to eight fictitious patients with subclinical hypothyroidism. We investigated (1) whether variation in physician's preference was observable and to what extent it was explained by characteristics of GPs and their patient populations and (2) whether the data were compatible with deterministic and stochastic monotonicity assumptions.Results: Levothyroxine prescriptions varied substantially among the 526 responding GPs. Between-GP variance in levothyroxine prescriptions (logit scale) was 9.9 (95% confidence interval: 8.0, 12) in the initial mixed effects logistic model, 8.3 (6.7, 10) after adding a fixed effect for country and 8.2 (6.6, 10) after adding GP characteristics. The occurring prescription patterns falsified the deterministic monotonicity assumption. All cases in all countries were more likely to receive levothyroxine if a different case of the same GP received levothyroxine, which is compatible with the stochastic monotonicity assumption. The data were incompatible with this assumption for a different definition of the instrument.Conclusions: Our study supports the existence of physician's preference as a determinant in treatment decisions. Deterministic monotonicity will generally not be plausible for physician's preference as an instrument. Depending on the definition of the instrument, stochastic monotonicity may be plausible.