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SNHP 6000 (Ari) - Research for the Health Professions: Research Design

Types of Study Designs

A way of combining data from many different research studies. A meta-analysis is a statistical process that combines the findings from individual studies.  ExampleAnxiety outcomes after physical activity interventions: meta-analysis findings.  Conn V.  Nurs Res. 2010 May-Jun;59(3):224-31.

Systematic Review
A summary of the clinical literature. A systematic review is a critical assessment and evaluation of all research studies that address a particular clinical issue. The researchers use an organized method of locating, assembling, and evaluating a body of literature on a particular topic using a set of specific criteria. A systematic review typically includes a description of the findings of the collection of research studies. The systematic review may also include a quantitative pooling of data, called a meta-analysis.  ExampleComplementary and alternative medicine use among women with breast cancer: a systematic review.  Wanchai A, Armer JM, Stewart BR. Clin J Oncol Nurs. 2010 Aug;14(4):E45-55.

Randomized Controlled Trial
A controlled clinical trial that randomly (by chance) assigns participants to two or more groups. There are various methods to randomize study participants to their groups.  ExampleMeditation or exercise for preventing acute respiratory infection: a randomized controlled trial.  Barrett B, et al. Ann Fam Med. 2012 Jul-Aug;10(4):337-46.

Cohort Study (Prospective Observational Study)
A clinical research study in which people who presently have a certain condition or receive a particular treatment are followed over time and compared with another group of people who are not affected by the condition.  Example: Smokeless tobacco cessation in South Asian communities: a multi-centre prospective cohort study. Croucher R, et al. Addiction. 2012 Dec;107 Suppl 2:45-52.

Case-control Study
Case-control studies begin with the outcomes and do not follow people over time. Researchers choose people with a particular result (the cases) and interview the groups or check their records to ascertain what different experiences they had. They compare the odds of having an experience with the outcome to the odds of having an experience without the outcome.  ExampleNon-use of bicycle helmets and risk of fatal head injury: a proportional mortality, case-control study Persaud N, et al.  CMAJ. 2012 Nov 20;184(17):E921-3.

Cross-sectional study
The observation of a defined population at a single point in time or time interval. Exposure and outcome are determined simultaneously.  ExampleFasting might not be necessary before lipid screening: a nationally representative cross-sectional study.  Steiner MJ, et al.  Pediatrics. 2011 Sep;128(3):463-70.

Case Reports and Series
A report on a series of patients with an outcome of interest. No control group is involved.  ExampleStudents mentoring students in a service-learning clinical supervision experience: an educational case report.  Lattanzi JB, et al.  Phys Ther. 2011 Oct;91(10):1513-24.

Ideas, Editorials, Opinions
Put forth by experts in the field.  Example: Health and health care for the 21st century: for all the people. Koop CE.  Am J Public Health. 2006 Dec;96(12):2090-2.

Animal Research Studies
Studies conducted using animal subjects.  Example: Intranasal leptin reduces appetite and induces weight loss in rats with diet-induced obesity (DIO).  Schulz C, Paulus K, Jöhren O, Lehnert H.  Endocrinology. 2012 Jan;153(1):143-53.

Test-tube Lab Research
"Test tube" experiments conducted in a controlled laboratory setting.

Adapted from Study Designs. In NICHSR Introduction to Health Services Research: a Self-Study Course. and Glossary of EBM Terms. 

Levels of Evidence

The EVIDENCE PYRAMID is often used to illustrate the development of evidence. At the base of the pyramid is animal research and laboratory studies - this is where ideas are first developed. As you progress up the pyramid the amount of information available decreases in volume, but increases in relevance to the clinical setting.  Adaptation of the Evidence Pyramid Diagram developed by the Medical Research Library of Brooklyn, SUNY Downstate Medical Center.

Sources of research may be either pre-appraised (summaries), primary literature or more anecdotal.

Type of Study Where to Find it
Systematic Reviews or Meta-analysis Cochrane Library, MEDLINE, EMBASE
Critically-Appraised Topics DynaMed, UpToDate
Critically-Appraised Articles ACP Journal Club
Randomized Controlled Trials Original articles (search MEDLINE, EMBASE)
Cohort Studies Original articles (search MEDLINE, EMBASE)
Case-Controlled Studies etc. Original articles (search MEDLINE, EMBASE)
Background Info/Expert Opinion Books, editorials