Residual Confounding in Observational Studies

نویسندگان

  • Keith B. Greenland
  • Shiroh Isono
  • Satoru Tsuiki
چکیده

To the Editor:—I read the study by Fellahi JL et al. titled “Perioperative use of dobutamine in cardiac surgery and adverse cardiac outcome” with great interest. This study showed that the use of dobutamine was associated with adverse outcomes in adult cardiac surgery, and the authors concluded that these results suggest that dobutamine should only be administered when the benefit is judged to outweigh the risks. Although the study is interesting and the results are provocative, we need to be careful how to examine these results before we conclude that these results suggest that dobutamine may be harmful. First, we can be sure from the data of this observational study that the group of patients who received dobutamine was sicker in both left ventricular function and EURO score. Therefore, it is vital to know whether the propensity score (probability of using dobutamine) was a significant variable in the second method of logistic regression analysis when the propensity score was used as a separate covariate. If propensity score was a significant variable in determining adverse outcome after cardiac surgery in the logistic regression analysis, it would suggest that residual confounding due to “selection bias” caused by using dobutamine in a sicker group of patients was still present, despite the propensity score was used in the multivariate analysis. We definitely need this data to be sure whether any residual confounding was present, and if residual confounding is present, it may at least, in part, explain the results why the use of dobutamine was associated with a poorer outcome. Furthermore, the authors should also discuss the possibility of residual confounding from omitting confounders as a limitation of an observational study. Second, the conclusion of only using dobutamine when benefit is judged to outweigh the risks is not helpful to both practicing anesthesiologists and researchers. The data presented in this study showed that dobutamine was used predominantly in patients with a lower ejection fraction or those with left ventricular dysfunction in their cohort. This practice will remain unchanged in many cardiothoracic centers after knowing the results of this study because this is the group of cardiac patients most likely to have benefits from the use of dobutamine. I believe a more appropriate, balanced, and constructive conclusion from the data of this study is that an adequately powered randomized controlled trial is needed to clarify the risks and benefits of dobutamine in patients with different degrees of left ventricular function in adult cardiac surgery.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Methodological issues of confounding in analytical epidemiologic studies

Background: Confounding can be thought of as mixing the effect of exposure on the risk of disease with a third factor which distorts the measure of association such as risk ratio or odds ratio. This bias arises because of complex functional relationship of confounder with both exposure and disease (outcome). In this article, we provided a conceptual framework review of confounding issues in epi...

متن کامل

Assessment and control for confounding by indication in observational studies.

In the evaluation of pharmacologic therapies, the controlled clinical trial is the preferred design. When clinical trial results are not available, the alternative designs are observational epidemiologic studies. A traditional concern about the validity of findings from epidemiologic studies is the possibility of bias from uncontrolled confounding. In studies of pharmacologic therapies, confoun...

متن کامل

Frequency and impact of confounding by indication and healthy vaccinee bias in observational studies assessing influenza vaccine effectiveness: a systematic review

BACKGROUND Evidence on influenza vaccine effectiveness (VE) is commonly derived from observational studies. However, these studies are prone to confounding by indication and healthy vaccinee bias. We aimed to systematically investigate these two forms of confounding/bias. METHODS Systematic review of observational studies reporting influenza VE and indicators for bias and confounding. We asse...

متن کامل

The impact of residual and unmeasured confounding in epidemiologic studies: a simulation study.

Measurement error in explanatory variables and unmeasured confounders can cause considerable problems in epidemiologic studies. It is well recognized that under certain conditions, nondifferential measurement error in the exposure variable produces bias towards the null. Measurement error in confounders will lead to residual confounding, but this is not a straightforward issue, and it is not cl...

متن کامل

Mendelian randomisation meta-analysis sheds doubt on protective associations between 'moderate' alcohol consumption and coronary heart disease.

Context A protective association between low-dose alcohol and risk of coronary heart disease (CHD) has been suggested by meta-analyses of observational studies and experimental studies. Observational studies are, however, vulnerable to residual confounding and selection bias. Compared with observational studies, the Mendelian randomisation (MR) approach can mitigate confounding, is immune to re...

متن کامل

Estimation of average causal effect using the restricted mean residual lifetime as effect measure.

Although mean residual lifetime is often of interest in biomedical studies, restricted mean residual lifetime must be considered in order to accommodate censoring. Differences in the restricted mean residual lifetime can be used as an appropriate quantity for comparing different treatment groups with respect to their survival times. In observational studies where the factor of interest is not r...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2009