Letters to the Editor

Systematic Reviews Provide More Accurate Assessments


Am Fam Physician. 2005 Jul 15;72(2):226.

to the editor: In her article, “Omega-3 Fatty Acids,”1 in American Family Physician, Dr. Covington provides a thorough review of omega-3 fatty acids. A challenge for readers, however, is deciding how to change their practice based on a review. Reviews describe the included studies but often not their quality. In addition, the selection of references in a review may create a bias. These issues are addressed by performing a systematic review, which attempts to rigorously examine, evaluate, and synthesize all relevant studies on a given topic.

As one example of a different conclusion reached by a review and a systematic review, Dr. Covington described studies that reported improvement in patients with rheumatoid arthritis who take omega-3 fatty acids. However, a recent systematic review2 found no significant improvement in pain, swollen joint count, or patient global assessment in those taking omega-3 fatty acids.

This systematic review2 was one of a series on omega-3 fatty acids developed by the Agency for Healthcare Research and Quality’s Evidence-based Practice Centers Program in partnership with the National Institutes of Health Office of Dietary Supplements. Reports also have been released on omega-3 fatty acids and other topics such as cardiovascular disease, cancer, type 2 diabetes, asthma, mental health, organ transplantation, and cognitive function. These can be accessed online athttp://www.ahrq.gov/clinic/epcix.htm. Reports on maternal and child health and eye health care are in progress. Compared with narrative reviews, systematic reviews such as these can provide a more accurate assessment of the evidence for an intervention’s safety and efficacy.


1. Covington MB. Omega-3 fatty acids. Am Fam Physician. 2004;70:133–40.

2. Newberry SJ. Effects of omega-3 fatty acids on lipids and glycemic control in type II diabetes and the metabolic syndrome and on inflammatory bowel disease, rheumatoid arthritis, renal disease, systemic lupus erythematosus, and osteoporosis. Agency for Healthcare Research and Quality, U.S. Dept. of Health and Human Services, 2004. Rockville, Md.: Evidence report/technology assessment no. 89; AHCPR publication no. 04-E012–02.

editor’s note: This letter was sent to the author of “Omega-3 Fatty Acids,” who declined to reply.


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This series is coordinated by Kenny Lin, MD, MPH, Associate Deputy Editor for AFP Online.



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