AGA probiotic guideline reveals shortage of high-quality data



The role of probiotics in the management of gastrointestinal disorders remains largely unclear, according to a clinical practice guideline published by the American Gastroenterological Association (AGA).

Out of eight disorders reviewed by the guideline panel, four had enough relevant data to support conditional recommendations, while the other four were associated with knowledge gaps that precluded guidance, reported lead author Grace L. Su, MD, AGAF, of the University of Michigan, Ann Arbor, and colleagues.

“It is estimated that 3.9 million American adults used some form of probiotics or prebiotics ... in 2015, an amount which is four times that in 2007,” the guideline panelists wrote. Their report is in Gastroenterology. “Given widespread use and often biased sources of information, it is essential that clinicians have objective guidance for their patients about the appropriate use of and indications for probiotics.”

The creation of such guidance, however, proved a challenging task for the panel, who faced an “extremely varied” evidence base.

Dr. Su and colleagues, who were selected by the AGA Governing Board and Clinical Guidelines Committee, encountered “differences in the strain of microbe(s) used, dose, and route of administration.”

They noted that such differences can significantly affect clinical outcomes.

“Within species, different strains can have widely different activities and biologic effects,” they wrote. “Many immunologic, neurologic, and biochemical effects of gut microbiota are likely not only to be strain specific, but also dose specific. Furthermore, combinations of different microbial strains may also have widely different activity as some microbial activities are dependent on interactions between different strains.”

Beyond differences in treatments, the investigators also reported wide variability in endpoints and outcomes, as well as relatively small study populations compared with pharmacological trials.

Still, data were sufficient to provide some conditional recommendations.

The guideline supports probiotics for patients with pouchitis, those receiving antibiotic therapy, and preterm/low-birthweight infants. In contrast, the panel recommended against probiotics for children with acute infectious gastroenteritis, noting that this recommendation differs from those made by other medical organizations.

“While other society guidelines have previously recommended the use of probiotics in [children with acute infectious gastroenteritis], these guidelines were developed without utilizing GRADE methodology and also relied on data outside of North America which became available after the recommendations were made,” wrote Dr. Su and colleagues. They described a moderate quality of evidence relevant to this indication.

In comparison, the quality of evidence was very low for patients with pouchitis, low for those receiving antibiotics, and moderate/high for preterm/low-birthweight infants.

For Clostridioides difficile infection, Crohn’s disease, ulcerative colitis, and irritable bowel syndrome, the panel recommended probiotics only in the context of a clinical trial, citing knowledge gaps in these areas.

They also noted that probiotics may not be suitable for those at high risk of infection.

“[F]or patients who place a high value on avoidance of potential harms, particularly those with severe illnesses or immunosuppression, it would be reasonable to select not to use probiotics,” the panelists wrote.

Concluding their discussion, Dr. Su and colleagues called for more high-quality research.

“We identified that significant knowledge gaps exist in this very promising and important area of research due to the significant heterogeneity between studies and variability in the probiotic strains studied,” they wrote. “The lack of consistent harms reporting makes it difficult to assess true harms. The lack of product manufacturing details prohibits true comparisons and decreases the feasibility of obtaining certain products by patients. Future high-quality studies are urgently needed which address these pitfalls.”

According to the panelists, the probiotic guideline will be updated in 3-5 years, or possibly earlier if practice-altering findings are published.

The investigators disclosed relationships with Nestex, AbbVie, Takeda, and others.

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