Division of General Medicine and Clinical Epidemiology, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America.
PLoS One. 2013 May 7;8(5):e63973. doi: 10.1371/journal.pone.0063973. Print 2013.
Channeling occurs when a medication and its potential comparators are selectively prescribed based on differences in underlying patient characteristics. Drug safety advisories can provide new information regarding the relative safety or effectiveness of a drug product which might increase selective prescribing. In particular, when reported adverse effects vary among drugs within a therapeutic class, clinicians may channel patients toward or away from a drug based on the patient's underlying risk for an adverse outcome. If channeling is not identified and appropriately managed it might lead to confounding in observational comparative effectiveness studies.
To demonstrate channeling among new users of second generation antipsychotics following a Food and Drug Administration safety advisory and to evaluate the impact of channeling on cardiovascular risk estimates over time.
Florida Medicaid data from 2001-2006.
Retrospective cohort of adults initiating second generation antipsychotics. We used propensity scores to match olanzapine initiators with other second generation antipsychotic initiators. To evaluate channeling away from olanzapine following an FDA safety advisory, we estimated calendar time-specific propensity scores. We compare the performance of these calendar time-specific propensity scores with conventionally-estimated propensity scores on estimates of cardiovascular risk.
Increased channeling away from olanzapine was evident for some, but not all, cardiovascular risk factors and corresponded with the timing of the FDA advisory. Covariate balance was optimized within period and across all periods when using the calendar time-specific propensity score. Hazard ratio estimates for cardiovascular outcomes did not differ across models (Conventional PS: 0.97, 95%CI: 0.81-3.18 versus calendar time-specific PS: 0.93, 95%CI: 0.77-3.04).
Changes in channeling over time was evident for several covariates but had limited impact on cardiovascular risk estimates, possibly due to unmeasured confounding. Although calendar time-specific propensity scores appear to improve covariate balance, the impact on comparative effectiveness results is limited in this setting.
当药物及其潜在的对照药物根据患者潜在特征的差异进行选择性处方时，就会发生通道现象。药物安全性警示可能会提供有关药物产品相对安全性或有效性的新信息，这可能会增加选择性处方。特别是，当报告的不良反应在治疗类别内的药物之间存在差异时，临床医生可能会根据患者发生不良后果的潜在风险，将患者引导至某种药物或远离某种药物。如果未识别并适当处理通道现象，可能会导致观察性比较有效性研究中的混杂。
展示在食品和药物管理局安全性警示后第二代抗精神病药新使用者的通道现象，并评估随时间推移对心血管风险估计的影响。
2001-2006 年佛罗里达州医疗补助数据。
启动第二代抗精神病药的成年人的回顾性队列。我们使用倾向评分将奥氮平启动者与其他第二代抗精神病药启动者相匹配。为了评估食品和药物管理局安全性警示后奥氮平的通道现象，我们估计了特定于日历时间的倾向评分。我们比较了这些特定于日历时间的倾向评分与传统估计的倾向评分在心血管风险估计中的表现。
对于某些，但不是所有心血管风险因素，都可以看到对奥氮平的通道现象减少，并且与 FDA 咨询的时间相对应。在使用特定于日历时间的倾向评分时，在时期内和所有时期内都优化了协变量平衡。心血管结局的风险比估计值在模型之间没有差异（传统 PS：0.97，95%CI：0.81-3.18 与特定于日历时间的 PS：0.93，95%CI：0.77-3.04）。
随着时间的推移，几个协变量的通道现象发生了变化，但对心血管风险估计的影响有限，这可能是由于未测量的混杂。尽管特定于日历时间的倾向评分似乎改善了协变量平衡，但在这种情况下，对比较有效性结果的影响有限。
