This systematic review was conducted in accordance with the JBI methodology for systematic reviews of prevalence and incidence [
8] with the updated guideline of the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA 2020) [
9] (Supplemental Table
1).
Eligibility criteria
The inclusion criteria for this review and meta-analysis were: all critically ill children with an age group of under 18 years old; studies that had been conducted and reported in English; articles with a publicly available full text; and observational studies (cross-sectional, case-control, cohort studies, and longitudinal studies). However, studies that did not define the age of participants (above 18-year-old age group), studies without publicly available full-text, studies in languages other than English, studies that duplicated published literature, and studies that could not extract important outcome data were excluded.
Search strategy
The search strategy aimed to locate both published and unpublished studies. The international databases PubMed/MEDLINE, CINAHL/EBSCO, HINARI, and Google Scholar were accessed to find relevant articles. A Medical Subject Headings (MeSH), keyword terms and phrases were used both in separation and in combination using the Boolean operators “OR” and “AND” to search for eligible articles. The reference list of all included sources of evidence was screened for additional studies. The task of searching sources was carried out from all stated electronic databases performed during August 29–31, 2022.
With the MeSH terms, “Malnutrition” and “Critical Illness*”, the keywords and phrases: “Malnutrition”, “Nutritional Deficienc*, “Under nutrition”, “Under-nutrition”, “Undernutrition”, “Wasting”, “Malnourishment”, “undernourishment”, “Malnourished”, “Nutrition deficienc*”, “Hypo nutrition*”, “Nutritional disorders*”, “Critical Illness*”, “Illness, Critical”, “Illnesses, Critical”, “Critically Ill”, “Intensive Care”, “Care, Critical”, “ICU Patient*”, “Care, Intensive”, “ICU Intensive Care”, “children”, “pediatrics”, ‘‘preschool children’’, prevalence, incidence, magnitude, burden, and proportion were used in separation or in combination to retrieve relevant articles on malnutrition in critically ill children.
Study selection
Two impartial reviewers looked over the titles and abstracts before comparing them to the inclusion criteria. The JBI System for the Unified Management, Assessment and Review of Information (JBI SUMARI) (JBI, Adelaide, Australia) was used to extract potentially pertinent papers in their entirety and import their citation information [
10]. Two independent reviewers thoroughly evaluated the complete text of the chosen citations in relation to the inclusion criteria. Discussion was used to settle any discrepancies that arose between the reviewers at each level of the selection process.
Outcome operational definition
The term malnutrition refers to any type of alteration of the nutritional status and includes nutritional deficiencies, obesity, and the use of inappropriate diets. However, in this article, the term is typically used to refer to nutritional deficiencies (undernutritions).
Data were extracted from studies included in the review by two independent reviewers using the standardized data extraction tool for prevalence and incidence available in JBI SUMARI [
12]. The extracted data includes specific details about the condition, populations, study methods, measured outcome, and description of the main result. Any disagreements that arose between the reviewers were resolved through discussion.
Publication bias and heterogeneity
Heterogeneity was assessed statistically using the standard chi-squared and I squared tests. When I
2 exceeds 75%, high heterogeneity was declared [
13] and a subgroup analysis was conducted to manage heterogeneity among studies using measurements including income level and study design. The possible risk of publication bias was examined by inspection of the funnel plot and statistically using Egger’s regression test. Besides, a sensitivity analysis was performed to examine the influence of a single study on the overall estimate.
Data synthesis
The extracted data were pooled in a statistical proportional meta-analysis using JBI SUMARI. Effect sizes were expressed as a proportion with 95% confidence intervals around the summary estimate. The adjusted odds ratio (AOR) with its upper and lower bounds was extracted for significant variables. Statistical analyses were performed using the Freeman-Turkey Transformation with a random effects model. Further analysis was done with STATA 17.0 statistical software. Additionally, sub-group analysis, publication bias, and sensitivity analysis were performed.