Gray literature: An important resource in systematic reviews

Paez A. Gray literature: An important resource in systematic reviews.
J Evid Based Med. 2017 Aug; 10(3):233-2

Systematic reviews are publications that provide a state-of-art synthesis of evidence on any given research question.

While clinical trials and large studies are analysed to synthesize evidence, you cannot afford to ignore gray literature. The concept of Gray literature is described in this article as “that which is produced on all levels of government, academics, business and industry in print and electronic formats, but which is not controlled by commercial publishers”. Simply put, gray literature comprises the whole collection of research works that have not been published.

In this article, Arsenio Paez discusses the importance and overall positive contributions gray literature has to offer, for a systematic review. It will give you an understanding of how gray literature is an unbiased source of information which will help you balance your research work. He describes sources of gray literature, benefits of its use, an illustrative sample, constraints and an overall implication of its necessity.

Paez uses studies from different authors to explain how you will understand that gray literature is a tool for providing information not available otherwise, because it is not commercially published. He highlights major issues with commercial research – unreported clinical trials, lengthy submission procedures, vague data, lag and rejection. You will learn what constitutes publication bias, and how gray literature counters the same.

The sample study on the prevalence and effects of growth hormone (GH) deficiency after traumatic brain injury (TBI) will give you an idea of why you need gray literature in your quest for information. In particular, Paez talks of one study “anterior pituitary hormone replacement in TBI,” which has been completed and presented in conferences but is not a part of published material. The study provides detailed information on outcome measures, eligibility, interventions and contact regarding the effect of GH replacement therapy on physical and neuropsychological function in TBI patients with documented abnormalities. You could potentially contact the study author and get in touch with information or investigators otherwise unavailable to you. Ultimately, as Paez writes, it enriches the evidence base for your systematic review. The scope here is huge.

It is an interesting and informative read, and will aid you when you plan to author a systematic review.

So, don’t forget to check out gray literature, when authoring a systematic review, and also when looking for research information. Go ahead and learn something new!

Credits for locating this article to my colleague Swapnali Patil

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