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This tutorial will show you how to answer a simple evidence-based medicine etiology or harm question in Ovid MEDLINE. This type of
question helps you identify risk factors or causes for a disease or disorder, including iatrogenic harm, or problems that might arise
from medical treatment for another condition. The example question I am going to use is “do children who have received the measles-mumps
-rubella vaccine have a higher chance of developing autism?” To answer this question, I need to find an article that examines the risk for
this disorder. Although finding a randomized controlled trial on the topic would be nice, harm questions are usually answered by cohort or
case control studies. To enter Ovid, start on the Library home page and scroll down the “Quick Links” dropdown list on the left side of the page.
Choose “MEDLINE (Ovid)”. The easiest way to structure a search is to put one concept on each line and then combine them. Our first
concept is the vaccine exposure, so I will type “MMR vaccine” into the box and click on “Search”. Ovid will try to match what I typed with
one of its predetermined keywords, called Medical Subject Headings (MeSH) terms. What I want matches perfectly with one of the MeSH
terms, so I will check the box next to “Include All Subheadings” and click on “Continue”. Subheadings help you narrow down your search
results, but they are not always needed for basic searches. I now have the first line of my search. I will enter my second concept, autism,
and click on “Search”. Ovid matches this to “Autistic Disorder”. If you are ever matched to a term you are unsure about, you can click on the
“i” on the right side of the screen to get more information about the MeSH term. I know this is what I want, so I will just include all the
subheadings again and continue back to the main page. So I have my two concepts, but I need to add something to my search to limit it
to articles that talk about harm. The best way to do this is to search for the word “risk” in the article record. I will enter “risk$.tw” into the
search box and click on “Search”. The dollar sign tells Ovid I want to retrieve both the plural and singular forms of the word, and the “dot tw”
tells Ovid to look for the word within the text of the record. The highest level of evidence that can be found to answer an etiology or harm
question is usually a cohort study. I will do a search for cohort studies and add that MeSH heading to my searches. Now I need to combine
all the lines of my search by clicking on the boxes in front of each line or on the top box to automatically include them all, and then clicking
on “And” to tell Ovid I want a search with all four terms. For this topic, I did find some cohort studies. If I had not, I would go back and
combine just the first three search lines and look for a case control study. I will now scroll down my results set. The second article looks
like an appropriate choice to answer my question.