Multidisciplinary Delphi consensus statement on minimal standards for clinical metadata and end points in microbiome studies.

The lack of harmonisation for microbiome-based clinical studies represents a critical issue for microbiome researchers and stakeholders, although microbiome research and clinical studies on the gut microbiome have been intensively conducted for more than a decade.

The two-round Delphi survey, conducted within the framework of the Horizon Europe Human Microbiome Action (HMA) consortium, aimed to standardise metadata collection, sampling procedures, data generation and sharing, and standard operating procedures for aspects of gut microbiome-based clinical studies beyond outcomes. On the basis of the outcome, the HMA consortium provided 15 recommendations that might be taken up by the community at large to promote coherence and harmonisation in the way microbiome clinical research is and will be performed. The recommendations cover the areas of anthropometric metadata, bioclinical metadata, pre-analytical standards, sample collection and processing, and clinical end points.

Advancing knowledge and introducing standardised guidelines for the management and setup of future clinical studies using microbiome next-generation technologies is an essential step toward improving data analysis and interpretation and supporting the most appropriate strategies to diagnose and cure diseases. In the proposed Delphi process, a consensus was reached for the majority of the treated topics addressed, although the resulting recommendations still require scientific validation.

Key points from the publication:

• Need for greater harmonisation and standardisation: There is a clear need to improve consistency across clinical microbiome studies, particularly regarding anthropometric and bioclinical data, pre-analytical standards, sample collection and processing, and clinical end points.
• Establishment of recommendations:  A total of 15 recommendations were developed to promote greater coherence and harmonisation in microbiome research.
• Future implementation and validation: Given the high level of consensus achieved, adoption of these recommendations is strongly advisable to help standardise future microbiome-based clinical studies. However, scientific validation remains necessary.

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Schierwagen, R., Carraturo, F., Iyappan, A. et al. Multidisciplinary Delphi consensus statement on minimal standards for clinical metadata and end points in microbiome studies. Nat Rev Gastroenterol Hepatol (2026). https://doi.org/10.1038/s41575-026-01229-1