5 “A”s of Evidence-based Medicine & PICOTS: Using “Population, Intervention, Comparison, Outcomes, Timing, Setting” (PICOTS) In Evidence-Based Quality Improvement Work

5 “A”s of Evidence-based Medicine & PICOTS: Using “Population, Intervention, Comparison, Outcomes, Timing, Setting” (PICOTS) In Evidence-Based Quality Improvement Work

Much of what we do when answering key clinical questions can be summarized using the 5 “A” EBM Framework—Ask, Acquire, Appraise, Apply and “A”s Again.[1] Key clinical questions create the focus for the work and, once created, drive the work or project. In other words, the 5 “A”s form a scaffolding for us to use in doing EB quality improvement work of many types.

When healthcare professionals look to the medical literature for answers to various clinical questions or when planning comparative reviews, they frequently utilize checklists which employ the mnemonics, PICO (population, intervention, comparison, outcome)[2], PICOTS (same as PICO with the addition of timing and setting) or less frequently PICOT-SD (which also includes study design.[3]  PICOTS (patient population, intervention, comparison, outcomes, timing and setting) is a checklist that can remind us of important considerations in all of the 5 “A” areas.

PICOTS in Forming Key Clinical Questions and Searching

PICOTS is a useful framework for constructing key questions, but should be applied thoughtfully, because at times all PICOTS elements are not needed to construct a useful clinical question. For example, if I am interested in the evidence regarding prevention of venous thromboembolism in hip replacement surgery, I would want to include the population and study design and perhaps key outcomes, but I would not want to limit the question to any specific interventions in case there are some useful interventions of which I am not aware. So the question might be, “What is the evidence that thromboembolism or deep vein thrombosis (DVT) prophylaxis with various agents reduces mortality and clinically significant morbidity in hip replacement surgery?” In this case, I was somewhat specific about P (the patient population—which frequently is the condition of interest—in this case, patients undergoing  hip replacement surgery), less specific about O (mortality and morbidities) and not specific about I and C.

I could be even more specific about P if I specified patients at average risk for VTE or only patients at increased risk. If I were interested in the evidence about the effect of glycemic control on important outcomes in type II diabetes, I might pose the question as, “What is the effect of tight glycemic control on various outcomes,” and type in the terms “type 2 diabetes” AND “tight glycemic control” which would not limit the search to studies reporting outcomes of which I was unaware.

Learners are frequently taught to use PICO when developing search strategies. (When actually conducting a search, we use “condition” and not “population” because the condition is more likely to activate the MeSH headings in PubMed which produces a search with key synonyms.) As illustrated above, the PICO elements chosen for the search should frequently be limited to P (the patient population or condition) and I so as to capture all outcomes that have been studied. Therefore, it is important to remember that many of your searches are best done with using only one or two elements and using SD limits such as for clinical trials in order to increase the sensitivity of your search.

PICOTS in Assessing Studies for Validity and Synthesizing Evidence

When critically appraising studies for reliability or synthesizing evidence from multiple studies, PICOTS reminds us of the areas where heterogeneity is likely to be found. PICOTS is also useful in comparing the relevance of the evidence to our population of interest (external validity) and in creating decision support for various target groups.

PICOTS in Documenting Work

Transparency can be made easier by using PICOTS when documenting our work. You will notice that many tables found in systematic reviews and meta-analyses include PICOTS elements.


1. Modified by Delfini Group, LLC (www.delfini.org) from Leung GM. Evidence-based practice revisited. Asia Pac J Public Health. 2001;13(2):116-21. Review. PubMed PMID: 12597509.

2. Richardson WS, Wilson MC, Nishikawa J, Hayward RS. The well-built clinical question: a key to evidence-based decisions. ACP J Club. 1995;123:A12–3.

3. Methods Guide for Effectiveness and Comparative Effectiveness Reviews. AHRQ Publication No. 10(12)-EHC063-EF. Rockville, MD: Agency for Healthcare Research and Quality. April 2012. Chapters available at: www.effectivehealthcare.ahrq.gov.


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