Blais L, Ernst P, Suissa S
Department of Epidemiology and Biostatistics, McGill Pharmacoepidemiology Research Unit, McGill University, Montreal, Canada.
Am J Epidemiol. 1996 Dec 15;144(12):1161-9. doi: 10.1093/oxfordjournals.aje.a008895.
A previously published nested case-control study, the Saskatchewan Asthma Epidemiologic Project (SAEP) spanning 1980-1987, investigated the risk of fatal or near fatal asthma and found different risks for two inhaled beta 2-agonists, fenoterol and salbutamol. The authors assessed whether this comparison was confounded by indication because of channeling of inhaled fenoterol to more severely afflicted asthmatics. Using three subcohorts selected from a cohort of 12,301 asthmatics assembled from the computerized databases of Saskatchewan Health and followed over 7 years, the authors studied two forms of channeling and investigated whether greater asthma severity and less well-controlled disease were associated with preferential prescribing of a first prescription of inhaled fenoterol, as opposed to inhaled salbutamol, and whether they were associated with the likelihood of a switch from inhaled salbutamol to fenoterol as well as a switch from inhaled fenoterol to salbutamol. The authors found that the initial choice between fenoterol and salbutamol was independent of the severity of the asthma and disease control, but that preferential prescribing of fenoterol occurred among users of salbutamol who showed signs of increased severity or uncontrolled asthma. The switch from inhaled fenoterol to salbutamol was, however, minimally related to asthma severity. They conclude that the comparison between inhaled fenoterol and salbutamol in the SAEP may have been biased by indication. This study demonstrates that long-term information on medication use is essential to ensure that the results of such case-control studies are not biased by indication.
一项先前发表的巢式病例对照研究——萨斯喀彻温省哮喘流行病学项目（SAEP），涵盖1980年至1987年，调查了致命或近乎致命哮喘的风险，并发现两种吸入型β2激动剂（非诺特罗和沙丁胺醇）存在不同风险。作者评估了这种比较是否因将吸入型非诺特罗用于病情更严重的哮喘患者而存在适应证混杂因素。作者从萨斯喀彻温省卫生部计算机数据库中收集的12301名哮喘患者队列中选取了三个亚队列，并对其进行了7年的随访，研究了两种形式的用药选择偏向，并调查了哮喘病情更严重和疾病控制较差是否与优先开具吸入型非诺特罗而非吸入型沙丁胺醇的首剂处方有关，以及它们是否与从吸入型沙丁胺醇转换为非诺特罗以及从吸入型非诺特罗转换为沙丁胺醇的可能性有关。作者发现，非诺特罗和沙丁胺醇之间的初始选择与哮喘的严重程度和疾病控制无关，但在沙丁胺醇使用者中，非诺特罗的优先处方发生在病情加重或哮喘未得到控制的患者中。然而，从吸入型非诺特罗转换为沙丁胺醇与哮喘严重程度的关系最小。他们得出结论，SAEP中吸入型非诺特罗和沙丁胺醇之间的比较可能因适应证而存在偏差。这项研究表明，关于药物使用的长期信息对于确保此类病例对照研究的结果不会因适应证而产生偏差至关重要。
