Searching for a Consensus Among Inflammatory Bowel Disease Studies: A Systematic Meta-Analysis

Area of Science:

• Microbiome research
• Gastroenterology
• Inflammatory Bowel Disease (IBD)

Background:

• Numerous studies have investigated the gut microbial ecology in Crohn's disease (CD) and ulcerative colitis (UC).
• However, findings regarding IBD-associated taxa and ecological effect sizes lack consistency across studies.
• This variability complicates the understanding of IBD pathogenesis and microbiome-based diagnostics.

Approach:

• A systematic literature search of PubMed and Google Scholar was conducted.
• A meta-analysis of 13 studies was performed to evaluate the impact of sample types (stool, biopsy, lavage) on IBD gut microbiome research.
• Uniform bioinformatic methods were applied to all primary data for standardized analysis.

Key Points:

• Reduced alpha diversity was a consistent finding in both CD and UC, more pronounced in CD.
• While disease significantly influenced beta diversity, sample type had a greater effect size than the disease itself.
• Fusobacterium was the most consistently identified genus in CD, but other disease-associated genera varied significantly between studies.
• Stool-based studies exhibited lower heterogeneity compared to biopsy-based studies, particularly for CD.

Conclusions:

• Sample type variation is a critical factor contributing to inconsistencies in IBD gut microbiome studies.
• Careful consideration of sample type during study design is essential for robust and reproducible research.
• Stool samples are recommended over biopsy samples for CD studies due to lower heterogeneity, leading to more reliable results.