Riis Anders H, Johansen Martin B, Jacobsen Jacob B, Brookhart M Alan, Stürmer Til, Støvring Henrik
Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus N, Denmark.
Pharmacoepidemiol Drug Saf. 2015 May;24(5):478-85. doi: 10.1002/pds.3738. Epub 2015 Jan 20.
The aim of this study was to quantify the effect of the look back period on the misclassification of new users of antibiotics and asthma medications.
We included all children born in Denmark from 1995 through 2006 and all prescriptions of antibiotics and asthma medication from 1995 through 2011. The study period was 2007 through 2011. True new users redeemed their first prescription in the study period whereas prior users redeemed their first prescription before the study period. Look-back periods ranged from 30 days up to 12 years prior to the study period, and we defined new users as those without a prescription in the look-back period. The relative misclassification (RM) was estimated as the number of defined new users divided by the number of true new users.
For antibiotics, the RM decreased from 4.75 for look-back periods of 30 days to 2.36 for 2 years and 1.33 for 5 years. For asthma medication, the RM decreased from 2.53 for look-back periods of 30 days to 1.48 for 2 years and 1.20 for 5 years. Older age, male gender, and absence of treatment-related diagnoses were associated with higher RM.
Studies applying the new user design are strongly dependent on the available information on prescriptions. For drug classes with intermittent use such as asthma medications, even a 2-year look-back period produced severe misclassification. Excluding children with a prior treatment-related diagnosis can reduce the level of misclassification.
本研究旨在量化回顾期对抗生素和哮喘药物新使用者错误分类的影响。
我们纳入了1995年至2006年在丹麦出生的所有儿童，以及1995年至2011年所有抗生素和哮喘药物的处方。研究期为2007年至2011年。真正的新使用者在研究期内兑换了他们的第一张处方，而先前使用者在研究期之前兑换了他们的第一张处方。回顾期从研究期前30天到12年不等，我们将新使用者定义为在回顾期内没有处方的人。相对错误分类（RM）估计为定义的新使用者数量除以真正的新使用者数量。
对于抗生素，RM从回顾期30天的4.75降至2年的2.36和5年的1.33。对于哮喘药物，RM从回顾期30天的2.53降至2年的1.48和5年的1.20。年龄较大、男性以及没有与治疗相关的诊断与较高的RM相关。
应用新使用者设计的研究强烈依赖于处方的可用信息。对于如哮喘药物等间歇性使用的药物类别，即使2年的回顾期也会产生严重的错误分类。排除有先前与治疗相关诊断的儿童可以降低错误分类的程度。
