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Evidence Based Practice: ACCESS

Type of Question and Type of Study

Not all levels of evidence are created equal. Depending on the type of question you ask, some study types will be more appropriate than others to use as evidence.

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What Does this Mean?

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  • The library does not have access to this article through our online subscriptions
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Evidence Cycle: Access evidence in the journal literature

Levels of Evidence

In clinical research, the quality of your evidence is important. The stronger your research evidence is, the less potential for bias exists.

However, you also have to consider the probability of a topic having an abundance of articles in some of the categories.

For example, a new drug therapy for a rare disease that came out within the last year will not have many randomized controlled trials (RCTs) yet. Perhaps the trials are still ongoing. Without enough RCTs, there cannot be a systematic review written.

Secondary Research

Authors systematically identify, select, evaluate, and synthesize all high-quality primary research in order to answer a focused clinical question. A meta-analysis uses statistical methods to combine data from studies included in a systematic review.

Identifying Systematic Reviews

Look for words like 'systematic review' or 'meta-analysis' and a methods section that details the search strategy and inclusion criteria used to locate research included in the study. 


Schönenberger KA, Schüpfer AC, Gloy VL, et al. Effect of Anti-Inflammatory Diets on Pain in Rheumatoid Arthritis: A Systematic Review and Meta-Analysis. Nutrients. 2021;13(12):4221. Published 2021 Nov 24. doi:10.3390/nu13124221

Secondary Research

Guidelines provide a summary of the relevant medical literature. Professional societies develop guidelines to aid clinicians in choosing diagnostic tests, treatments for specific conditions, etc. 

Identifying Evidence-based Practice Guidelines

Look for 10 or more authors and 'practice guideline' in the title of the article.


Anderson J, Caplan L, Yazdany J, et al. Rheumatoid arthritis disease activity measures: American College of Rheumatology recommendations for use in clinical practice. Arthritis Care Res (Hoboken). 2012;64(5):640-647. doi:10.1002/acr.21649

Primary Research

A scientific experiment where patients are divided into two groups. One group receives treatment and the other receives a placebo. 

Identifying Randomized Controlled Trials 

Look for a methods section in the article's headings and words like 'randomized' and 'placebo.'


Vadell AKE, Bärebring L, Hulander E, Gjertsson I, Lindqvist HM, Winkvist A. Anti-inflammatory Diet In Rheumatoid Arthritis (ADIRA)-a randomized, controlled crossover trial indicating effects on disease activity. Am J Clin Nutr. 2020;111(6):1203-1213. doi:10.1093/ajcn/nqaa019

Primary Research

An observational study where patients are followed over time to investigate causes of disease and to establish risk factors or health outcomes. 

  • A cohort study can be prospective, where a group is studied from a point of exposure and followed into the future to view outcomes. 
  • A cohort study can also be retrospective where a group is studies from the present outcome and the past is studied to locate exposures.

Identifying Cohort Studies

Look for 'cohort' or a group studied over a number of years and a section called 'methods.'


Liu Q, Hebert JR, Shivappa N, et al. Inflammatory potential of diet and risk of incident knee osteoarthritis: a prospective cohort study. Arthritis Res Ther. 2020;22(1):209. Published 2020 Sep 10. doi:10.1186/s13075-020-02302-z

Primary Research

Studies that report in-depth on a patient or group of patients with the same, rare, disease. 

Identifying Case Studies

Look for words like 'case report' or 'case study.'


Zhang H, Kong F, Yu F, Hao S. First report of rheumatoid arthritis and secondary Sjögren's syndrome complicated with heart failure. Clin Case Rep. 2021;9(8):e04581. Published 2021 Aug 11. doi:10.1002/ccr3.4581

Secondary Research OR Tertiary Resource

No empirical evidence is provided. A group of experts provide recommendations based on experience and authoritative sources. 

Identifying Secondary Research

Look for words like 'review' or authors summarizing other articles. They will often not contain a methods section. 


Gioia C, Lucchino B, Tarsitano MG, Iannuccelli C, Di Franco M. Dietary Habits and Nutrition in Rheumatoid Arthritis: Can Diet Influence Disease Development and Clinical Manifestations?. Nutrients. 2020;12(5):1456. Published 2020 May 18. doi:10.3390/nu12051456

Primary Research

Researchers perform experiments on cell cultures, tissue, and animals to find treatments for human disease.

Identifying Primary Research

Look for words like 'rats,' 'mice,' and other animals or collected samples, with 'experiment' and a section heading called methods.


Shi N, Zhang S, Silverman G, Li M, Cai J, Niu H. Protective effect of hydroxychloroquine on rheumatoid arthritis-associated atherosclerosis. Animal Model Exp Med. 2019;2(2):98-106. Published 2019 Apr 19. doi:10.1002/ame2.12065

Not Research

Narrative information about a real person or incident. A story or recounting of an event. Not a formal article. 

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