[MUSIC] Hi everyone. It's Kay Dickersin again, and we're going to continue in our discussion about systematic reviews, and meta-analysis. I'm going to start out with a refresher on standards for systematic reviews. In the past it's really been every person for him or herself about what makes a good systematic review. It's amazing how slowly the world moves as I mentioned in the very first lecture for this class. In the old days, we did review articles any way we wanted. No one taught us how to do them, but we knew the general idea was to review the literature for a particular question or set of questions. And then during the 80s and more like the 90s for the field of medicine and public health, people started saying, hey, we should do these reviews systematically. It's a double standard requiring certain minimum standards for the primary research that we review, and then not to care how we do the review ourselves. And so for that reason we move towards doing reviews systematically. That is they have a method section, a results section, and a discussion section. Standards have gradually risen and these standards that I'm showing on this slide, shows that the institute of medicine came out in 2011 with standards for systematic reviews, how to do them. And this is welcome because systematic reviews are proliferating in literature and most of them don't follow any set standard, so it appears people are just doing whatever the next guy in their field did. So, let's just briefly review some of these standards for systematic reviews. And in particular I'm going to be interested in how to manage the bias of doing the systematic review, how to minimize that bias. It's not bias in the individual studies that are being reviewed, but bias in the process of doing the review itself. What you see on this slide is a cover of a book called Standards for Systematic Reviews, that was published by the Institute of Medicine in 2011. And the Institute of Medicine gathered together a group of experts in the field of medicine, public health, systematic reviews and other topics, and asked them to help it develop a series of standards that others and anyone interested in doing or assessing a systematic review would follow. Some of those standards relate to minimizing bias in a systematic review, and that's what we're going to be focusing on today. In this slide, I show you the first steps of initiating a systematic review. But in that case, we aren't really talking directly about minimizing bias in that systematic review. Of course, we want to be careful to minimize the conflicts of interest sitting around the table, and those who are providing input to the systematic review. But that's not what we're going to be spending a lot of time on today. On the next slide, we start getting into how to minimize bias in a systematic review. Perhaps the most important step in a systematic revue in terms of minimizing bias is to find and assess the individual studies. One might imagine if all published studies were a random sample of all studies ever done for a particular question. That just doing a quick look in a filling cabinet or search of PubMed, might give you a sample of all studies ever done and a comprehensive search for studies would not be necessary. However, it is and I'm going to show you some of the data backing up that claim. Comprehensive systematic search for the evidence has to be done. And then, action has to be taken so that we address the problem of potentially biased research results reporting. I'm going to talk about this and managing the data collection, and how it relates to bias in a systematic review. The following two slides are other standards for doing a systematic review, but we aren't really going to talk about this today, when we're talking about metabias. We will talk about these topics in other context, however. This is how to report a systematic review. Again, we'll just touch on this briefly. So finally to sum up the topics that I've covered in Section A. Is that there can be bias in conducting a systematic review; and what we're going to call this in this lecture is metabias. We've already talked about bias and the methods that are used in the included studies in the systematic review in an earlier lecture. Today though, we're going to be talking about bias in the methods used in doing the systematic review itself, or metabias. If you want to read more about this, there's an article from Analysts of Internal Medicine 2010 and the first author is Steve Goodman. I'm the second author. And this talks about metabias and a little bit more about it, if it's a topic that interests you. There are three forms of medibias that I'm going to talk about today. Selection biases, information bias, and bias in the analysis, or analysis bias. And we're going to take these one by one in the following sections.