On 2017 Mar 15, Michelle Fiander commented:

My comment on this paper pertains to the authors' methodology and rationale for it. This paper is not a systematic review and it does not claim to be, but it describes its literature search as systematic, refers to duplicate screening, and includes a study flowchart--each of which are part of systematic review methodology.

Despite describing its lit search as 'systematic,' there is insufficient detail to reproduce the strategies or to confirm the number of results identified and screened for the review. Table 1 which is not a flowchart but is labeled "Flowchart of all clinical studies included for the final analysis" implies that terms i-v, and "secondary" terms were combined using Boolean OR to create two sets of concepts which were then combined using Boolean AND. If this is the case, the search finds about 100 in Pubmed; 87 in Embase, 7 in Cochrane, 1690 in Google Scholar, 32,200 in Science Direct (sciencedirect.com), and 8 articles and 9 book chapters in Springer Link (springerlink.com). These numbers do not correspond with the number of citations retrieved per Table 1.

In terms of how references were screened and studies selected for inclusion, the authors describe the process as follows: "Study eligibility was assessed independently by two observers and all assessments were then crosschecked." What is absent here are the stages at which duplicate screening occured, e.g. title/abstract? full-text? both? Further, with dual screening there are typically conflicts, but we are not told how they are resolved.

Systematic reviews are popular; some might say they are "flavor of the ....decade." Perhaps it is this popularity that has led to a glut of poor quality systematic reviews in the literature. Whatever the reason, using the adjective 'systematic' to describe one or two aspects of a review in the absence of a full and complete systematic approach does, I suspect, contribute to misunderstandings of the purpose, process and value of true systematic reviewing and evidence synthesis.

On 2017 Mar 15, Michelle Fiander commented:

My comment on this paper pertains to the authors' methodology and rationale for it. This paper is not a systematic review and it does not claim to be, but it describes its literature search as systematic, refers to duplicate screening, and includes a study flowchart--each of which are part of systematic review methodology.

Despite describing its lit search as 'systematic,' there is insufficient detail to reproduce the strategies or to confirm the number of results identified and screened for the review. Table 1 which is not a flowchart but is labeled "Flowchart of all clinical studies included for the final analysis" implies that terms i-v, and "secondary" terms were combined using Boolean OR to create two sets of concepts which were then combined using Boolean AND. If this is the case, the search finds about 100 in Pubmed; 87 in Embase, 7 in Cochrane, 1690 in Google Scholar, 32,200 in Science Direct (sciencedirect.com), and 8 articles and 9 book chapters in Springer Link (springerlink.com). These numbers do not correspond with the number of citations retrieved per Table 1.

In terms of how references were screened and studies selected for inclusion, the authors describe the process as follows: "Study eligibility was assessed independently by two observers and all assessments were then crosschecked." What is absent here are the stages at which duplicate screening occured, e.g. title/abstract? full-text? both? Further, with dual screening there are typically conflicts, but we are not told how they are resolved.

Systematic reviews are popular; some might say they are "flavor of the ....decade." Perhaps it is this popularity that has led to a glut of poor quality systematic reviews in the literature. Whatever the reason, using the adjective 'systematic' to describe one or two aspects of a review in the absence of a full and complete systematic approach does, I suspect, contribute to misunderstandings of the purpose, process and value of true systematic reviewing and evidence synthesis.