 When using PubMed, you may find the number of results that it retrieves to be overwhelming. Remember, PubMed contains over 30 million citations. It would not be uncommon to have PubMed retrieve well over 10,000 results on a topic. In fact, searching for the concept cancer yields over 4 million results. Luckily, there are strategies that you can use in PubMed to refine your results and make them more manageable and relevant to your needs. In this lecture, we'll discuss PubMed filters and field tags, looking at how they can be used to narrow and focus your results. While I'm focusing on PubMed, it's worth mentioning that most biomedical databases such as M-Base, Synol, and Psych Info offer their own set of filters and field tags as well. Let's start by talking about PubMed filters, which not only allow you to narrow your results, but also enable you to focus your search without adding additional terms. Continuing with our search on the relationship between cell phones and cancer, we want articles that focus on children and are from the last 15 years. We can use the filters for both of these criteria. First, complete your search in PubMed. Then, look to the left-hand side of the results screen. To limit to the last 15 years, use the date slider and adjust it to 2005. Doing this will automatically adjust your results' date range. Alternatively, you can scroll down to the publication date filter and limit to articles from the last year, last 5 years, or last 10 years. If we want to limit the results to those that focus on children, we need to scroll down on the sidebar and click on the additional filters box and then click the age filters. Here, you'll also see additional ways that you can filter your search. A few popular options are article type and language. For our search, click on age and then select the specific ages that you'd be interested in. I'm going to click on the child birth to 18 years, child 6 to 12 years, and adolescent 19 to 24. Next, I'll click on the show button. Now these filters show up on the filter sidebar. Clicking on the box next to child 6 to 12 years limits the search to the specific age group. If I want to try a different age group, I can unclick this box and then click on a different option such as young adults 19 to 24. One more thing that I'll point out about filters is that if you're looking for high quality articles, you can use the article type category to quickly narrow your results to publication types that are considered high levels of evidence. For example, I can narrow my search on cancer to reviews in order to find summaries of multiple studies on a particular kind of cancer. Or I can limit to randomized controlled trials, which is considered the strongest form of study design for evaluating interventions and diagnostic tests about cancer. One feature that I find frustrating that's important to note is that the filters that I turn on will remain on even if I move to a different search. To turn them off, click on the clear all link just above the results or on the reset all filters button on the bottom of the sidebar. I'll finish talking about filters with a word of warning. If you want to find the newest articles and or if you're conducting an exhaustive and comprehensive search such as a systematic review, you'll want to be very careful about using filters. While filters are perfect for quickly narrowing and focusing a search when you need a small set of articles on a topic, using just about any of the filters available in PubMed will automatically exclude the most recent articles published. That's because most of the filters rely on mesh terms to work. Therefore articles that haven't been indexed yet will automatically be excluded. Also the coding behind the filters isn't immediately obvious so it makes it difficult to report your search strategy in a way that can be easily replicated by others. Thus when doing an exhaustive and comprehensive search it's recommended to use search terms instead of filters. For example, if our search was being used for a systematic review, rather than using the age filter I might search for children by including the following mix of mesh and keywords. The mesh child or child with an asterisk or youth with an asterisk. Like filters, field tags are also helpful for quickly accessing a few relevant articles. But on like filters, field tags are standardly used when conducting a systematic review. A field tag is a special tag or code that is typed at the end of the search term. The tag goes in brackets and tells PubMed exactly what fields to search. For example, I would type Osler William Bracket AU Bracket to tell PubMed to look for articles written by William Osler. To better understand how field tags work let's briefly talk about the default fields that PubMed automatically searches. When you type a search term in the PubMed search box for example the term cancer, PubMed defaults to looking in all fields. This means it retrieves results if the word cancer occurs in any field such as the title, author name, author affiliation, journal name, abstract, language, mesh terms, or author supplied keywords. This is certainly a more thorough way to search but it can lead to a large set of results and a higher chance of retrieving off topic results. For example, this article on Seminella came up when I searched by cancer because it was written by an author whose name is J.L. Cancer. When you use field tags you're telling PubMed the exact fields to search rather than letting the database search in all of the fields. For systematic reviews the two most commonly used field tags are the TIAB and TW field tags. The TIAB tag tells PubMed to search for the terms in the title or abstract. So if we're looking for articles that discuss the relationship between mobile phones and cancer we can use the TIAB field tag to reduce our result numbers from around 1500 to 200. And from these 200 results most should be on the topic because we know that the citations either have the search terms in the title or they are mentioned in the abstract. If you want to be a bit more exhaustive in your search you can use the TW field tag. This tag searches the title and abstract but also includes the author supplied keywords in addition to many other fields. However, what's most important about the TW field tag is what it's not searching. It does not include author affiliation, author last name or journal name. These fields tend to retrieve the most off topic results. Not sure which to use? Test both options. With field tags there's some flexibility. If using TW captures relevant articles that you might otherwise miss you'll want to use this broader tag. If instead TW is causing a lot of noise you might want to tighten your search with the TIAB tag. This is where you might want to reach out to an informationist for advice on the best approach to take. When you only need a few relevant articles the TI field tag becomes extremely useful. It looks for results in which the search term appears in the title. When you're scoping the literature to get a sense of what's been published on your topic using TI is a great strategy to employ. For example, if I use TI after cancer and mobile phones my results go down to 23 and I'm only getting results where my search terms are in the titles. While you might miss out on articles that don't mention the terms in the titles this is a quick way to force relevant results to the top. Field tags are versatile and can be used with other search techniques. For example, I can develop my search and include nesting to group like terms together truncation to search for multiple endings and double quotes with my phrases along with the TI field tag. If you have trouble remembering what abbreviations to put in the brackets you can also apply field tags through PubMed's advanced search. Click on the advanced link underneath the PubMed search box. From here you can type your search terms and use the pull down menu next to all fields. In this menu select the field that you'd like to search. As soon as you add your search to the query box PubMed will add the proper formatting so you don't have to. At this point I've only skimmed the surface of what you can do with filters and field tags. If you would like to know more check out PubMed's user guide. Access it from the PubMed homepage by clicking on the FAQs and user guide link underneath the learn heading. For a full list of field tags visit this guide and click on the appendices link on the left hand side and then click on search field descriptions and tags. In closing it's important to remember that one of the reasons that PubMed is seen as a go-to database for biomedical literature is because of its extensive collection of citations. But if you find yourself in a situation where you need to narrow or refine your search filters and field tags are two search techniques that can help.