The impact of patient, intervention, comparison, outcome (PICO) as a search strategy tool on literature search quality: a systematic review




PICO Model, Search Strategy Tools, Literature Search, Evidence-Based Medicine, Systematic Reviews


Objective: This review aimed to determine if the use of the patient, intervention, comparison, outcome (PICO) model as a search strategy tool affects the quality of a literature search.

Methods: A comprehensive literature search was conducted in PubMed, Embase, CINAHL, PsycINFO, Cochrane Library, Web of Science, Library and Information Science Abstracts (LISA), Scopus, and the National Library of Medicine (NLM) catalog up until January 9, 2017. Reference lists were scrutinized, and citation searches were performed on the included studies. The primary outcome was the quality of literature searches and the secondary outcome was time spent on the literature search when the PICO model was used as a search strategy tool, compared to the use of another conceptualizing tool or unguided searching.

Results: A total of 2,163 records were identified, and after removal of duplicates and initial screening, 22 full-text articles were assessed. Of these, 19 studies were excluded and 3 studies were included, data were extracted, risk of bias was assessed, and a qualitative analysis was conducted. The included studies compared PICO to the PIC truncation or links to related articles in PubMed, PICOS, and sample, phenomenon of interest, design, evaluation, research type (SPIDER). One study compared PICO to unguided searching. Due to differences in intervention, no quantitative analysis was performed.

Conclusions: Only few studies exist that assess the effect of the PICO model vis-a-vis other available models or even vis-a-vis the use of no model. Before implications for current practice can be drawn, well-designed studies are needed to evaluate the role of the tool used to devise a search strategy.

 This article has been approved for the Medical Library Association’s Independent Reading Program.

Author Biographies

Mette Brandt Eriksen, University Library, University of Southern Denmark, Campusvej 55, 5230 Odense M


Tove Faber Frandsen, Department of Design and Communication, University of Southern Denmark, Universitetsparken 1, DK-6000 Kolding

Department of Design and Communication

Associate professor, PhD


Cochrane AL. 1931–1971: a critical review, with particular reference to the medical profession. Medicines Year. 2000:1–11.

Bastian H, Glasziou P, Chalmers I. Seventy-five trials and eleven systematic reviews a day: how will we ever keep up? PLOS Med. 2010 Sep 21;7(9):e1000326.

McGowan J, Sampson M, Salzwedel DM, Cogo E, Foerster V, Lefebvre C. PRESS Peer Review of Electronic Search Strategies: 2015 guideline statement. J Clinl Epidemiol. 2016 Jul;75:40–6.

Thomas J, McNaught J, Ananiadou S. Applications of text mining within systematic reviews. Res Synth Methods. 2011 Mar;2(1):1–14.

Evidence-Based Medicine Working Group. Evidence-based medicine. a new approach to teaching the practice of medicine. JAMA. 1992 Nov 4;268(17):2420–5.

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

Cooke A, Smith D, Booth A. Beyond PICO: the SPIDER tool for qualitative evidence synthesis. Qual Health Res. 2012 Oct;22(10):1435–43.

Booth A. Clear and present questions: formulating questions for evidence based practice. Libr Hi Tech. 2006;24(3):355–68.

Miller SA, Forrest JL. Enhancing your practice through evidence-based decision making: PICO, learning how to ask good questions. J Evidence-Based Dental Pract. 2001 Oct;1(2):136–41. DOI:

Higgins JP, Green S, eds. Cochrane handbook for systematic reviews of interventions. Wiley Online Library; 2008.

Huang X, Lin J, Demner-Fushman D, eds. Evaluation of PICO as a knowledge representation for clinical questions. AMIA Annu Symp Proc. 2006:359–63.

Considine J, Shaban RZ, Fry M, Curtis K. Evidence based emergency nursing: designing a research question and searching the literature. Int Emerg Nurs. 2017 May;32:78–82.

Higgins JPT, Green S, eds. Cochrane handbook for systematic reviews of interventions. Wiley Online Library; 2008. Lefebvre C ME, Glanville J. Chapter 6, Searching for studies.

Shea BJ, Grimshaw JM, Wells GA, Boers M, Andersson N, Hamel C, Porter AC, Tugwell P, Moher D, Bouter LM. Development of AMSTAR: a measurement tool to assess the methodological quality of systematic reviews. BMC Med Res Methodol. 2007 Feb 15;7:10.

Moher D, Liberati A, Tetzlaff J, Altman DG. Preferred reporting items for systematic reviews and meta-analyses: the PRISMA statement. PLOS Med. 2009 Jul 21;6(7):e1000097.

Booth A. How much searching is enough? comprehensive versus optimal retrieval for technology assessments. Int J Technol Assess Health Care. 2010 Oct;26(4):431–5.

National Institute for Health and Clinical Excellence. The guidelines manual [Internet]. London, UK: The Institute; Nov 2012 [cited 3 Jul 2018]. <>.

Buckland M, Gey F. The relationship between recall and precision. J Am Soc Inf Sci. 1994 Jan;45(1):12.

Munn Z, Stern C, Aromataris E, Lockwood C, Jordan Z. What kind of systematic review should I conduct? a proposed typology and guidance for systematic reviewers in the medical and health sciences. BMC Med Res Methodol. 2018 Jan 10;18(1):5.

Hjørland B. The foundation of the concept of relevance. J Am Soc Inf Sci Technol. 2010 Feb;61(2):217–37.

Agoritsas T, Merglen A, Courvoisier DS, Combescure C, Garin N, Perrier A, Perneger TV. Sensitivity and predictive value of 15 PubMed search strategies to answer clinical questions rated against full systematic reviews. J Med Internet Res. 2012 Jun 12;14(3):e85.

Hoogendam A, de Vries Robbe PF, Overbeke AJ. Comparing patient characteristics, type of intervention, control, and outcome (PICO) queries with unguided searching: a randomized controlled crossover trial. J Med Libr Assoc. 2012 Apr;100(2):121–6. DOI:

Methley AM, Campbell S, Chew-Graham C, McNally R, Cheraghi-Sohi S. PICO, PICOS and SPIDER: a comparison study of specificity and sensitivity in three search tools for qualitative systematic reviews. BMC Health Serv Res. 2014 Nov 21;14:579.

Higgins JP, Altman DG, Gotzsche PC, Juni P, Moher D, Oxman AD, Savovic J, Schulz KF, Weeks L, Sterne JAC. The Cochrane Collaboration’s tool for assessing risk of bias in randomised trials. BMJ (Clinical Research Ed). 2011 Oct 18;343:d5928.






Knowledge Synthesis