JPEN Journal Club 96. Scoping reviews

Two scoping reviews were published recently in JPEN,1, 2 so I thought that it would be appropriate to consider that topic now. Scoping reviews differ somewhat from systematic reviews. In systematic reviewing, one poses a particular question and then seeks the answer by identifying all of the relevant evidence in the medical literature. The process has been disseminated by the Cochrane Collaboration, which has developed a rigorous methodology designed to make any undertaking as transparent and unbiased as possible. That organization has even created continually updated online handbooks to guide anybody who wants to undertake a systematic review of interventions3 or of diagnostic tests.4 In addition to these Cochrane contributions, a 27-item checklist (the PRISMA [Preferred Reporting Items for Systematic Reviews and Meta-Analyses] 2020 statement) that itemizes the required steps is available.5 In a systematic review, the question being posed is relatively specific (eg, if a particular intervention is effective for a certain patient or if a particular test is reliable in diagnosing a certain disease). Scoping reviews have a different intent and are directed at a different audience. They are designed to enumerate the available evidence regarding a broader topic. Such reviews are not likely to provide clinicians with immediate information about one particular intervention or test. Rather, they are intended to be used by researchers who want to know where gaps of knowledge exist or by policy makers who need an overview of a particular field. Although the process of scoping has many similarities to systematic reviewing, there are some distinct differences besides the original posed question.6 Unlike systematic reviews with meta-analysis, no effort is made to synthesize or combine the data; a scoping review presents the state of the literature without attempting to draw any clinical conclusions. Consequently, no effort is made to critically appraise (eg, assessing risk-of-bias) the included studies. A wider variety of study designs may be included. There may be more emphasis on assessing the “gray literature” (conference abstracts, unpublished studies, non–peer reviewed papers, etc), so other databases, perhaps used less frequently in systematic reviews, become part of the search strategy; the inclusion of librarians on the team may be more important. The input of nonclinical stakeholders is likely to be more relevant. Conclusions may be more subjective, so preexisting beliefs and biases should be taken into account. Scoping reviews use some alternative terminology. Extracted data are “charted” not “tabulated.” When different members of the team chart the data, agreement between them is not assessed by “comparing” the numbers, but by a “calibration exercise.” The data are not “summarized” but “mapped.” The broader topic of interest is referred to as a “concept,” not as an “intervention” or “test.” “Context” refers to the details about the study population (eg, demographics, type of healthcare facility, etc). Finally, the PRISMA checklist was reworked to create a PRISMA Extension for Scoping reviews (PRISMA-ScR) containing 22 items.7 The five items that were removed from the original PRISMA checklist related to estimations from analyses of summary measures and assessments of risks of bias in the included studies. The two scoping reviews to be considered now relate to the role of dietitians in the intensive care unit (ICU)1 and to the effect of various nitrogen supplements (proteins or amino acids) in improving muscle strength and performance.2 The first one,1 by Terblanche et al from the United Kingdom, was published in the February 2025 issue of JPEN. Terblanche et al. began with two questions: what were the dietetic-led interventions in the ICU and did these influence outcomes? However, these investigators (all with dietetic backgrounds) believed that the ICU interventions by dietitians were already established, namely identifying and treating malnutrition, setting nutrition targets, designing nutrition support plans (including monitoring its delivery and informing the rest of the ICU team), developing and implementing guidelines, providing nutrition education, and using advanced practice skills such as inserting feeding tubes. Thus, they focused their attention on the second question, addressing both clinical (duration of ICU stay, mechanical ventilation, costs, mortality, complications, blood sugar control) and nutrition (initiation of nutrition support, energy and protein delivery, gastrointestinal side effects, use of parenteral nutrition, and appropriate dietetic referral) outcomes. They only considered randomized clinical trials (RCTs) and observational studies; abstracts, narrative reviews, editorials, and other types of gray literature were not sought. No language limitations were imposed. Nine databases were searched. Data were extracted in duplicate and disagreements resolved by discussion and consensus. The original investigators were contacted when necessary to clarify details or provide further information. A total of 732 studies were identified in the literature search and 39 additional ones were found elsewhere. After removing duplicates and assessing titles, abstracts, and full texts, 39 studies were included; only three of them were RCTs. The concepts (interventions) that were assessed in these 39 studies related to guidelines, individual nutrition treatments, and placing tubes. Associations were found in many, but not all, studies between an intervention and a favorable outcome. There also were seemingly discordant observations. For example, although critically ill patients who received more protein intake had better 90-day mortality in one observational study,8 one cluster-randomized RCT found no difference in the 28-day mortality when nutrition support algorithms designed by dietitians (and intended to maximize nutrient intake) were used rather than the usual delivery of nutrition support.9 Overall, the nutrition outcomes (eg, early initiation of nutrition support, energy and protein delivery) were more consistently improved by the intervention being assessed. Terblanche et al summarized the studies, along with some selected outcomes in each study, in a large (over four pages) table entitled “The dietetic-led interventions that influenced outcomes in adult critically ill patients.” It appeared outcomes lacking significant differences between groups in these studies were excluded from that table. Terblanche et al concluded that “Dietitian-led interventions improved nutrition outcomes and may have contributed to better clinical outcomes.” In the concluding paragraph of the paper, however, the authors did state, “Limitations include that the eligible studies were not graded for quality and no methodological assessment or risk of bias evaluation was performed; therefore, this review is not appropriate for use as evidence for a clinical guideline.” The second scoping review, by Al-Rawhani and five coworkers from Malaysia and Australia was published in the July 2025 issue of JPEN. These investigators began with an evidence-based presumption that protein supplementation increases muscle mass and strength and improves physical function. They then stated that not all proteins are the same and, as such, may have different effects. They also believed that it is unknown what the optimal amount of protein supplementation is. These quandaries led to the undertaking of this review. They searched five databases for RCTs that assessed the ability of protein and/or amino acid supplements to improve muscle-related outcomes (muscle strength, physical performance, body composition) in older adults (mean age >60 years). Screening of identified articles and data extraction were performed independently in duplicate. Included RCTs had to be peer-reviewed complete papers in English. The supplementation could be accompanied by resistance training (RT). The outcome data were grouped by the type of supplement used; there were 32 trials of whey protein, 12 of creatine, 11 of milk protein, eight of leucine, six of essential amino acids, four of soy protein, two of carnitine, two of citrulline, and one each of collagen peptide, l-arginine, and β-alanine. These 80 trials were relatively small; the median number of participants was 48. Most of them were from North America or Europe. Sixty-six trials had study durations of <6 months; 43 of these lasted ≤14 weeks. Space will not allow a detailed summary of all of the results. The results of the RCTs were not presented in a tabular format, but rather simply described in the text for each type of supplementation. As a result, it was difficult for me to discern trends; it did appear that the supplements, with or without RT, variably did or did not improve different outcomes. Al-Rawhani et al claimed that whey protein, creatine, and milk protein produced the best results when used along with RT and that leucine and milk protein may enhance body composition even if RT is not also provided. (As an aside, these conclusions would seem to be more appropriate in a systematic review.) My major concern with these (and likely other) scoping reviews relates to the manner in which evidence is considered. In both of these scoping reviews, the authors made good efforts to find all of the pertinent information, but in presenting the material that they uncovered, they just seemed to reiterate whatever it was that the original investigators reported. The process seems to minimize, if not completely disregard, levels of evidence and risks of bias. In other words, both sets of reviewers considered all of the studies to be equal in scientific value. For example, consider the two studies cited by Terblanche et al.1 that seemed to have found differences in survival regarding the intake of more protein.8, 9 On the one hand, observational studies can never establish causation; Weijs et al only found an association between better intake and better survival.8 An alternate explanation is that it is easier to deliver nutrients when a critically ill patient is healthier and it would not be surprising if healthier patients had better survival. On the other hand, Martin et al.9 reported a near significant (P = 0.058) benefit in the in-hospital mortality even though the longer-term mortality rates in those in both groups who survived that hospitalization were comparable. Readers would have been better informed if Terblanche et al had pointed all of this out to them. In summary, researchers and policy makers need to know not only what evidence is available but also what the scientific reliability of that evidence is. I can only hope that, in the future, authors of scoping reviews will rethink their policies and include critical appraisals of the studies that they discuss rather than just presuming that all evidence is equally compelling. You may have other thoughts about this paper. If so, I would encourage you to discuss them with your colleagues or even send an email to me ([email protected]). I would also again remind you that ASPEN has created an information kit with guidelines for how chapters, hospitals, and universities can develop their own journal clubs (www.nutritioncare.org/journalclub). For the next installment, please read the following article: Seifi N, Rezvani R, Sedaghat A, Nematy M, Khadem-Rezaiyan M, Safarian M. The effects of synbiotic supplementation on enteral feeding tolerance, protein homeostasis, and muscle wasting of critically ill adult patients: a randomized controlled trial. Trials. 2022;23(1):846. The author acknowledges the ongoing support of GIIssues Inc., a 501(c)(3) nonprofit organization dedicated to the practice and dissemination of evidence-based medicine. GIIssues Inc. supports educational expenses for the author as well as any expenses related to the creation of papers and other educational products. GIIssues Inc. does not provide any salary support to the author. There are no research materials that are related to this paper that can be accessed other than the stated references. None declared.