by Catholic University of the Sacred Heart

Credit: CC0 Public Domain

The gut microbiota might perhaps one day become a routine tool for the early diagnosis of many diseases and to guide treatment, but at present there is a lack of solid scientific evidence to support these claims. Yet, day by day, there are more and more offers of commercial kits for do-it-yourself testing, at the moment totally lacking in meaning and scientific solidity.

To put a stop to this drift, an international panel of experts, coordinated by Dr. Gianluca Ianiro, has drawn up 'instructions for use' for best practice in microbiota testing and recommendations for its indications, methods of analysis, presentation of results and potential clinical applications.

In a consensus paper published in Lancet Gastroenterology & Hepatology, the current knowledge gaps and future directions of research in this field are also recalled.

The aim of this paper is to provide a regulatory framework for the provision of microbiota tests and to reduce the use of inappropriate tests, in order to pave the way for an evidence-based development of human microbiota diagnostics in medicine.

The gut microbiota is a key mediator of a number of essential human functions: from metabolism to immune regulation to drug response. Imbalances in its composition ('dysbiosis') are also associated with various intestinal and extra-intestinal diseases and can influence the response to treatments (including cancer).

Although this field is still pioneering, there are already spin-offs in clinical practice. Microbiota manipulation, by means of fecal microbiota transplantation, for instance, is currently the routine treatment for relapses of Clostridioides difficile infection.

Several lines of research are evaluating the gut microbiota as a possible tool for diagnosis, prognosis, risk stratification and response to treatment.

In short, interest and enthusiasm abound, but valid scientific evidence is currently lacking, and future doctors are not taught in universities how to interpret a microbiota test, nor how to manipulate it for therapeutic purposes. But the market runs faster than science, as has already happened in the past with home genetic tests.

In order to give a rule to this new gold rush and define standards of quality and accuracy, a panel of international experts, led by Professors Antonio Gasbarrini and Giovanni Cammarota and Dr. Gianluca Ianiro of Fondazione Policlinico Gemelli (FPG)/Università Cattolica del Sacro Cuore (UCSC), among the absolute pioneers of microbiota research, drew up a consensus document.

"In recent years," recalls Dr. Serena Porcari of the Unit of Gastroenterology Fondazione Policlinico Gemelli and first author of the study, "the intestinal microbiota has taken on a key role as a diagnostic, prognostic and therapeutic tool. From this point of view, the first step, for a targeted modulation of the microbiota itself, is to obtain a standardization of its analysis, regulated according to the definition of minimum criteria for performing the test."

This initiative is aimed at establishing ethical, organizational and technical rules for the development, commercial use and clinical implementation of microbiota tests. The document is the result of a consensus of a multidisciplinary consortium of experts in this field, coordinated by Professor Gianluca Ianiro, including clinicians, bioinformaticians, microbial ecologists and clinical microbiologists.

The take-home message of the Consensus is that the time is not yet ripe to use microbiota analysis widely (outside highly specialized centers) in clinical practice, particularly for the early diagnosis of many diseases or as a guide to treatment.

"Further intervention studies are needed to evaluate the effectiveness of personalized (and not 'one-size-fits-all') modulation based on the results of these tests," says Professor Giovanni Cammarota, Professor of Gastroenterology, UCSC and Director of the FPG Gastroenterology Unit.

It is also necessary to educate the medical community to implement these tests in clinical practice."This document marks a decisive step towards a standardization that has become indispensable," argues Professor Antonio Gasbarrini, Dean of UCSC and Director of the Digestive Disease Center and of the Internal Medicine and Gastroenterology Unit—making the microbiota an increasingly integrated element in personalized medicine.

In the clinical context, such guidelines will be essential to translate research advances into concrete applications, improving the management of many microbiota-related gastroenterological and systemic diseases.

As Dean of the Faculty of Medicine at the Catholic University, I also believe that the proposed standardization represents a fundamental contribution not only to clinical practice and research, but also to innovative teaching in medical degree courses and post-graduate courses.

In fact, the recommendations put forward by the experts offer a solid and standardized scientific reference that can be immediately integrated into training programs to prepare doctors of the future to use microbiota testing in a critical and informed manner."

"This consensus document represents a crucial step towards bringing order to the current panorama of diagnostic tests on the intestinal microbiota," emphasizes Professor Maurizio Sanguinetti, Professor of Microbiology at the Catholic University of the Sacred Heart and Director of the Department of Laboratory and Hematological Sciences, Fondazione Policlinico Gemelli.

"The diagnostic characterization of the intestinal microbiota must be based on rigorous standards, in order to guarantee reliable and clinically useful results. It is not a simple laboratory test, but a complex tool that requires a deep understanding of microbial dynamics and their impact on human health.

"This is why these analyses must be conducted by highly qualified personnel with specific expertise in clinical microbiology and bioinformatics. In our Microbiology Laboratory at the Fondazione Policlinico Gemelli, we already apply diagnostic tests on the intestinal microbiota following the principles and best practices outlined in the document.

"It is essential to invest in the training of future physicians and microbiologists so that they acquire the necessary skills to correctly interpret the results of these tests and apply them effectively in clinical practice. This document provides a valuable basis to guide not only the current use of the tests, but also their future development, always with a view to evidence-based and personalized medicine."

More information: Serena Porcari et al, International consensus statement on microbiome testing in clinical practice, The Lancet Gastroenterology & Hepatology (2024). DOI: 10.1016/S2468-1253(24)00311-X

Journal information: The Lancet Gastroenterology & Hepatology 

Provided by Catholic University of the Sacred Heart