Commentary

Is complexity just too complex?

Nutrition interventions are often complex and multicomponent. Typical approaches to meta-analyses that focus on individual causal relationships to provide guideline recommendations are not sufficient to capture this complexity. The objective of this study is to describe the method of meta-analysis used for the Pediatric Weight Management (PWM) Guidelines update and provide a worked example that can be applied in other areas of dietetics practice. The effects of PWM interventions were examined for body mass index (BMI), body mass index z-score (BMIZ), and waist circumference at four different time periods. For intervention-level effects, intervention types were identified empirically using multiple correspondence analysis paired with cluster analysis. Pooled effects of identified types were examined using random effects meta-analysis models. Differences in effects among types were examined using meta-regression. Context-level effects are examined using qualitative comparative analysis. Three distinct types (or families) of PWM interventions were identified: medical nutrition, behavioral, and missing components. Medical nutrition and behavioral types showed statistically significant improvements in BMIZ across all time points. Results were less consistent for BMI and waist circumference, although four distinct patterns of weight status change were identified. These varied by intervention type as well as outcome measure. Meta-regression indicated statistically significant differences between the medical nutrition and behavioral types vs the missing component type for both BMIZ and BMI, although the pattern varied by time period and intervention type. Qualitative comparative analysis identified distinct configurations of context characteristics at each time point that were consistent with positive outcomes among the intervention types. Although analysis of individual causal relationships is invaluable, this approach is inadequate to capture the complexity of dietetics practice. An alternative approach that integrates intervention-level with context-level meta-analyses may provide deeper understanding in the development of practice guidelines.

To describe and compare, through a scoping review, emerging knowledge synthesis methods for integrating qualitative and quantitative evidence in health care, in terms of expertise required, similarities, differences, strengths, limitations, and steps involved in using the methods.

Electronic databases (e.g., MEDLINE) were searched, and two reviewers independently selected studies and abstracted data for qualitative analysis.

In total, 121 articles reporting seven knowledge synthesis methods (critical interpretive synthesis, integrative review, meta-narrative review, meta-summary, mixed studies review, narrative synthesis, and realist review) were included after screening of 17,962 citations and 1,010 full-text articles. Common similarities among methods related to the entire synthesis process, while common differences related to the research question and eligibility criteria. The most common strength was a comprehensive synthesis providing rich contextual data, whereas the most common weakness was a highly subjective method that was not reproducible. For critical interpretive synthesis, meta-narrative review, meta-summary, and narrative synthesis, guidance was not provided for some steps of the review process.

Some of the knowledge synthesis methods provided guidance on all steps, whereas other methods were missing guidance on the synthesis process. Further work is needed to clarify these emerging knowledge synthesis methods.