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What is a primary source?

A primary source is a document or record which reports a study, experiment, event or other phenomenon firsthand. Primary sources are usually written by the person(s) who did the research, conducted the study, ran the experiment, or witnessed the event.

Primary Sources include:

  • pilot/prospective studies
  • cohort studies
  • survey research
  • case studies
  • qualitative studies
  • clinical trials and  randomized clinical trials/RCTs
  • double blind method

Example from CINAHL:

Hormone therapy and venous thromboembolism among postmenopausal women: impact of the route of estrogen administration and progestogens: the esther study. Canonico M; Oger E; Plu-Bureau G; Conard J; Meyer G; Levesque H; Trillot N; Barrellier MT; Wahl D; Emmerich J; et al.; Estrogen and Thromboembolism Risk (ESTHER) Study Group; Circulation, 2007 Feb 20; 115 (7): 840-5 (journal article - clinical trial, research)

Abstract: BACKGROUND: Oral estrogen therapy increases the risk of venous thromboembolism (VTE) in postmenopausal women. Transdermal estrogen may be safer. However, currently available data have limited the ability to investigate the wide variety of types of progestogen. METHODS AND RESULTS: We performed a multicenter case-control study of VTE among postmenopausal women 45 to 70 years of age between 1999 and 2005 in France. We recruited 271 consecutive cases with a first documented episode of idiopathic VTE (208 hospital cases, 63 outpatient cases) and 610 controls (426 hospital controls, 184 community controls) matched for center, age, and admission date. After adjustment for potential confounding factors, odds ratios (ORs) for VTE in current users of oral and transdermal estrogen compared with nonusers were 4.2 (95% CI, 1.5 to 11.6) and 0.9 (95% CI, 0.4 to 2.1), respectively. There was no significant association of VTE with micronized progesterone and pregnane derivatives (OR, 0.7; 95% CI, 0.3 to 1.9 and OR, 0.9; 95% CI, 0.4 to 2.3, respectively). In contrast, norpregnane derivatives were associated with a 4-fold-increased VTE risk (OR, 3.9; 95% CI, 1.5 to 10.0). CONCLUSIONS:Oral but not transdermal estrogen is associated with an increased VTE risk. In addition, our data suggest that norpregnane derivatives may be thrombogenic, whereas micronized progesterone and pregnane derivatives appear safe with respect to thrombotic risk. If confirmed, these findings could benefit women in the management of their menopausal symptoms with respect to the VTE risk associated with oral estrogen and use of progestogens.

Subjects: Hormone Replacement Therapy; Thromboembolism; Venous Thrombosis; Venous Thromboembolism; Aged: 65+ years; Middle Aged: 45-64 years; Female

Primary Sources

Finding Primary
Publication Type: Select Clinical Trial and Randomized Clinical Trial.
(Hold down the CTRL key to select multiple items in the list)

Finding Primary
Select Advanced Search. Under Document Type: Select Case Study.

Finding Primary
Publication Type: Select Clinical Trial, Controlled Clinical Trial, and Randomized Clinical Trial.
(Hold down the CTRL key to select multiple items in the list)

Finding Primary
From the search results screen, in the left column, under Article Type, click on "more . . ." Check the boxes next to Clinical Trial, Controlled Clinical Trial, and Randomized Controlled Trial.

What is a secondary source?

Secondary sources list, summarize, and evaluate primary information and studies so as to draw conclusions on or present our current state of knowledge in a discipline or subject. Sources may include a bibliography which may direct you back to the primary research reported in the article.

Secondary Sources include:

  • reviews, systematic reviews, meta-analysis
  • newsletters and professional news sources
  • practice guidelines & standards
  • clinical care notes
  • patient education Information
  • government & legal Information
  • entries in nursing or medical encyclopedias

Example from CINAHL:

Estrogen and stroke: a review of the current literature . Carwile E; Wagner AK; Crago E; Alexander SA; Journal of Neuroscience Nursing, 2009 Feb; 41 (1): 18-27 (journal article - CEU, exam questions, research,systematic review, tables/charts)

Abstract: Stroke is one of the leading causes of death and disability annually, and one of the larger populations for which neuroscience nurses care. Differences in gender have been identified as a risk factor for stroke repeatedly throughout the literature. The purpose of this evidence-based literature review is to provide information to healthcare professionals regarding stroke and its relationship with estrogen, the major female sex hormone. Background information on the three types of stroke is outlined, and information on estrogen compounds and hormone replacement therapy is detailed. A review of articles relating estrogen and/or hormone replacement therapy with stroke was performed. Fifty-seven articles met the criteria for inclusion in the review, 19 articles support the use of estrogen and/or an estrogen-related compound in the prevention or treatment of stroke, 6 articles claim estrogen and/or estrogen-related compounds are risk factors for stroke, and 11 articles remain inconclusive with regard to an estrogen and stroke relationship.

Subjects: Estrogens; Estrogens; Estrogens; Stroke; Female

Secondary Sources

Search Tip: Keep the search simple. If your topic is "Should women be given hormone replacement therapy" - search for Hormone Replacement Therapy.

Review the Systematic Reviews result column to find citations for systematic reviews, meta-analyses, reviews of clinical trials, evidence-based medicine, consensus development conferences, and guidelines.