Ganannan, Ciliska, & Thomas, (2010) explains that sometimes primary studies that were done may have been biased and the same primary studies used in conducting systematic literature reviews. This poses a problem in that it limits the process of conducting systematic literature reviews. Studies that are published and are biased when included in the systematic literature review will end up influencing the results of the review. This will mean that a research cycle that contains biased results will be published even after systematic literature review is done.
The problem of having a research cycle that produces bias evidence is accelerated by the fact that systematic literature review uses the primary sources for its review. Advancement in the world of technology has consequently affected the medical field and use of systematic literature review as a concept is disadvantage in its own. Most of the research findings are being published before a systematic literature review is conducted and released to consumers.
According to (Petticrew, & Roberts, 2006), even when systematic literature reviews are conducted on existing evidence, the reviews are already absolute even before being published. They become outdated before they are presented to the consumers making researchers involved in systematic literature reviews to constantly update their findings and include more research evidence that has been developed for they are unable to keep up with primary data developed almost on a daily basis.
Ganannan, Ciliska, & Thomas, (2010) argues that when authors are trying to obtain grant funding in primary healthcare research, it becomes a disadvantage to systematic literature review for researchers are using systematic literature reviews not for the benefit of the consumers but for their own benefit by coming up with results that suit grant funders. They have become greedy with money thereby generating results that suit the needs of those people who will fund grants of primary research in healthcare.
Systematic literature review differ form other research methodologies in that, other research methodologies do not use the careful systematic and logical steps followed in systematic literature reviews. Petticrew, & Roberts, (2006) explains that the predefined methodology of conducting systematic literature reviews gives the review its unique characteristic of transparency unlike primary studies which are not transparent.
Though literature and narrative reviews among other forms of review are useful, they do not produce findings which can be replicated. Systematic literature reviews findings can be replicated if the same procedure and methods used to arrive at the findings are used. The reviews under systematic literature are purely scientific unlike other literature reviews which may not place greater emphasis on scientific method of inquiry during investigations.
Furthermore, systematic literature reviews is a form of secondary study while literature reviews and other types of reviews are primary researches. In systematic literature reviews, the sources of reviews may be unknown to the researchers conducting the reviews while in other reviews like literature reviews; the researcher him/herself conducts the literature review. Systematic literature review methodologies are explicit in comparison with other research methodologies.
For instance, researchers in systematic literature review are experts who may have been hired to conduct the research and they therefore conduct the review with an open mind. They examine existing research methodologies and beliefs and in the process eliminate bias. To Petticrew, & Roberts, (2006) other research methodologies do not take into account existing research evidence and ends up incorporating individualized views and opinions in the research findings. Systematic reviews are also credited with consistency in their findings.
This is more especially because they generate conclusions that are not limited to only one study area and hence their ability to be generalized to other scenarios. In contrast with traditional literature reviews which use different methodologies in conducting the reviews, systematic reviews limit their studies to a single context that is same definitions of terms, same methods of measuring variable to be included in the study and same study designs among other factors.
Traditional reviews are not known to be explicit in their methodologies and thus the sharp contrast with systematic literature review. According to Petticrew, & Roberts, (2006) Systematic reviews are used when there is need to test accuracy of studies. Traditional reviews do not take into account existing research evidence and do not mostly follow the predetermined scientific method of investigating a study or a question and hence the accuracy of research findings via traditional literature review is poor.
Most researchers criticize traditional literature reviews as being conducted in a haphazard manner and having too many subjective opinions a characteristic that should be eliminated in research. Systematic reviews reflect reality for they do not incorporate individualized opinions and hence biasness is eliminated. They are therefore used when researchers want to know accuracy of certain studies or a question in research.