In this section of the EBM Express course, we'll be looking at how to search for the best evidence. Our learning objective for this section is to conduct an effective literature search to find the best evidence for our question. In earlier sections of EBM Express, we have learned about using the PICO format to build our search, about evidence taxonomies, and about where to search for evidence. Now we are ready to start putting these pieces together to find the evidence we need. We'll use an example question to walk through the process of searching for the best evidence. Our question is, what is the possible diagnosis in a pediatric patient admitted to the hospital for acute pancreatitis and subsequent development of alopecia and diarrhea? 

First, let's break out the concepts in our question like we did when we used the PICO format. First, we have a pediatric patient. Second, they have acute pancreatitis. Third, they have developed alopecia. Fourth, they have developed diarrhea. And finally, we are also specifically interested in a diagnosis. Let's use this search strategy chart to start developing our concepts into a search. The first concept I added was acute pancreatitis. I decided that a possible synonym to include might be pancreatitis in general without specifying acute. The second concept that I added was alopecia, which is a type of hair loss or baldness. So, I've added those to the chart as synonyms for this concept. Next, I added diarrhea, which has an alternate spelling. So, I've included that spelling on the chart. And the final entry on this chart is pediatric, which could also be expressed as child. If we had more details about the age of the patient, we might include more specific age designations like teenager or infant. But in our case, we do not have this information as part of our question. 

Remember that we are going to use Boolean logic to put the pieces of this chart into a search. Synonyms that read horizontally across the chart are put together with or and each concept that reads vertically down the chart is put together with and. You may also notice that I have not included diagnosis as a concept, but I will keep it in mind as we search for the evidence and look at our results. Translating our chart into search components gives us acute pancreatitis or pancreatitis and alopecia or hair loss or baldness and diarrhea or diarrhea and pediatric or child. Now that we have built a search, we need to decide where we want to search first. We have several options, but PubMed is frequently a great place to start for biomedical questions. It will likely have relevant results, plus it will give us a sense of how much literature is available to answer our question. So, let's open PubMed and start our searching. Remembering that we always want to start by searching each concept separately, let's add our acute pancreatitis concept to the search box and we'll click search.

This brings us to our results page and we can see we did receive quite a few results. So let's do a search for our second concept next which is alopecia and then we will click on our search button and again we get a very large search set. So let's click on advanced.

This takes us to the advanced search page where we can start combining our concepts. First, we're going to add alopecia to the query. And then we can add the acute pancreatitis concept. Since they're separate concepts, we're going to add with and. And now click on the search button.

Our results were dramatically reduced by combining the concepts, but we still have over 300. So, let's add a third concept. We can do that by typing into the search box once again for the concept of diarrhea. And then we're going to click on the search button, see our results, and go to the advanced search screen where we can take our first combined search and add the third concept. And again we'll add with and because it's a separate concept and click on the search button.

So at this point we are down to just 65 results which is maybe manageable but we have not yet added our fourth concept of pediatric or child and we could do that in the search box just like we did with the others. But frequently when you're looking at age related concepts, it's best to use filters which are available in PubMed and many other databases. So in PubMed, if we look on the left hand side, we have a list of filters and you'll immediately see several filters. But if we scroll down, you will also see that there are additional filters that we can use.

And within these filters is the age related filters and we are going to choose to click on child birth to 18 years. Now we can see across the top that that filter has been applied and that we have just four results. So at this point let's take a look at the four results.

When we look at these results, we find that we have three case reports which include a literature review and a mouse study within the reports and one drug evaluation article. So what do we think of these results? First, we might think these are not very high levels of evidence, especially when we are trying to answer a clinical question about diagnosis. And truthfully, a case report is not classified as a high level of evidence in any of the taxonomies that we learned about in the section on evidence taxonomies. However, you'll also remember that the highest levels of evidence don't always exist. So, these articles might be the best evidence available. When you come to the end of your search, you should always evaluate whether you are really done with searching. It is possible that you may find the exact answer at the highest possible level of evidence in your first search attempt. It is more likely, however, that you may want to consider adjusting and rerunning your search because you found too little, too much, or not the right content. In our example, we should consider running another search. 

Always remember that searching is an iterative process. So, if you are not happy or feel uncertain about the results you found, you should try adjusting your search using a different combination of your search concepts, fewer concepts, or maybe fewer or more filters. And you should consider using other resources like a different database or a different searching tool. Once you have spent the time figuring out your concepts, it is usually fairly easy to transfer your search to a different resource. In conclusion, when searching for the best evidence, start by breaking your question into concepts and think about synonyms. Then use Boolean logic to put the concepts together. Decide where to search and be sure to do your search in steps. You may also want to consider using filters. After you run the search, think about your results in terms of the evidence taxonomies and then evaluate and adjust. These are the basic steps to finding the best evidence. In future sections, we'll discuss some advanced searching techniques and some other tools that will help you in your search for the highest levels of evidence available for your question.