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Probiotics to Prevent Necrotizing Enterocolitis: Moving to Evidence-Based Use

/in ISAPP Science Blog /by KC

By Ravi Mangal Patel, MD, Msc, Associate Professor of Pediatrics, Emory University School of Medicine and Children’s Healthcare of Atlanta. rmpatel@nullemory.edu Twitter: @ravimpatelmd

Necrotizing enterocolitis (NEC) is one of the most lethal neonatal diseases, yet most people have never heard about it. The disease primarily affects preterm infants and is characterized by the development of intestinal inflammation. Clinically, the disease often manifests with an infant developing feeding intolerance or abnormal abdominal exam findings. The diagnosis is confirmed by abdominal x-ray or ultrasound. One of the key diagnostic radiographic findings is pneumatosis, which is air in the lumen of the bowel caused by gas-producing bacteria.

Dr Ravi Mangal Patel

NEC accounts for 1 out of every 10 deaths in US neonatal intensive care units. Among extremely preterm infants (those born at 22-28 weeks’ gestation) in the US, NEC is the most common single cause of death between 2 weeks and 2 months of age. Many infants with NEC undergo surgery to remove diseased bowel and those who recover and survive are at risk for long-term neurodevelopmental impairment and short bowel syndrome.

Decades of research into NEC have identified several key risk factors, including formula feeding, inconsistent feeding, abnormal intestinal oxygenation and [gut microbiota] dysbiosis. Studies have shown that dysbiosis, or abnormal intestinal colonization, is an important antecedent risk factor for the development of NEC. These studies have found that infants who develop NEC have an increase or bloom in the relative abundance of proteobacteria, compared to those who do not develop NEC. These proteobacteria, which contain a lipopolysaccharide coating, may lead to inflammation through their interaction with Toll-like receptor 4.

Given the role of dysbiosis in NEC, efforts to intervene by provision of probiotics to prevent NEC is a rational and extensively studied intervention, with over 63 randomized trials enrolling ~15,000 infants to date. The aforementioned meta-analysis, along with several others (Table 1), show probiotic supplementation results in large magnitude reductions in the risks of NEC and death and more modest reductions in the risks of late-onset sepsis. However, there is more limited data on extremely preterm infants and the quality or certainty of evidence for probiotics for the prevention of NEC was low in a recent Cochrane review.

 

Source: https://doi.org/10.1053/j.sempedsurg.2017.11.008

In the United States, an increasing number of centers have begun to routinely provide probiotics, with the greatest increase in use beginning in 2015. Observational studies evaluating routine probiotic use show benefits that are similar in magnitude to those from randomized trials, supporting the external validity of the results from the trials. This includes a large recent evaluation of probiotic use in the United States. Around the world, probiotic use is highly variable, from 100% of NICUs in New Zealand, 68% of NICUs in Germany, to 12% in the UK, 21% in Canada and 14% in the United States. Some of the variability in clinical use may be related to the uncertainty regarding the quality of commercially available probiotic products and need for clarity regarding strain-specificity of effects. There are many considerations both for and against routine use of probiotics to prevent NEC (Table 2). Current probiotic dietary supplements do not undergo FDA’s premarket review and approval requirements for safety and effectiveness or have to meet manufacturing and testing standards for drugs, and the potential risks were highlighted by a case of an infant death from a contaminated supplement. There is currently no FDA-approved live biotherapeutic product to prevent NEC.

Source: doi: 10.1016/j.earlhumdev.2019.05.009

Recent recommendations and guidance from ESPHGAN and the AGA also demonstrate that some medical organizations recognize the strength of the data in support of probiotic use to prevent NEC. It has been over two decades since the first study demonstrating the benefit of probiotic supplementation to prevent NEC in preterm infants. Now, more than ever, the evidence continues to accumulate regarding the beneficial effects of probiotic use in preterm infants as a compelling strategy to reduce the risks of both NEC and death. Therefore, considering the balance of potential risks and benefits including data from both randomized trials and routine implementation studies, my opinion is that the cumulative evidence to date supports routine probiotic use to prevent NEC and death in preterm infants.

As important is considering the parent voice regarding probiotic use. The NEC Society is a non-profit focused on NEC that has worked to incorporate the voice of the patient-family in clinical decisions.

Disclosures: Dr. Patel serves on the data-safety monitoring board of the Connection Study, which is a trial examining the use of an investigational probiotic to decrease the risk of NEC.

For further information, see this seminar by Dr. Patel: Practical Consideration for Probiotics in the NICU

stethoscope and keyboard

Interpreting Risk Reduction in Probiotic & Prebiotic Clinical Trials

/in featured, ISAPP Science Blog /by Mary Ellen Sanders

November 2017. By Prof. Michael Cabana MPH MD, Professor of Pediatrics, Epidemiology & Biostatistics and Chief, Division of General Pediatrics, University of California San Francisco.

Over the last few decades there has been a rapid acceleration in the number of published studies and clinical trials focused on probiotic and prebiotic interventions.  One common result that is reported is the change in risk of a condition or outcome after taking a probiotic or prebiotic supplement.  News articles and broadcasts commonly highlight claims in clinical trials (e.g., “this trial suggests a 33% reduction in X…).  However, in a world where news is sometimes transmitted in 140 characters or less, much nuance from a proper clinical trial can be lost. When assessing claims of risk reduction, it is important to evaluate and interpret these results in their proper context.  Here are a few tips.

What type of risk reduction is being reported?

When assessing the claims from a clinical trial, determine whether the claim is being presented as a relative risk reduction or an absolute risk reduction.  Sometimes the report may describe the risk of the outcome or disease directly compared to the normal incidence of the disease (i.e., incidence seen in the control group). This is a report of an absolute risk reduction. For example, if the control group had a 15% frequency of disease X and the probiotic group had a 10% frequency of disease X, then the absolute risk reduction is 5% (15%-10%=5%). Sometimes the report may describe a relative risk reduction, which is the % change between the risk in the probiotic group compared to risk in the control group. If the control group had a 15% frequency of disease X and the probiotic group had a 10% frequency of disease X, then the probiotic reduced your relative risk by 33% ([15%-10%]/15% = 5%/15% = 33%).

Is the risk reduction clinically significant?

If you notice that a relative risk reduction is being reported as statistically significant, you then need to ask yourself if the outcome is clinically significant. It is possible that a very large change in the relative risk reduction may not be clinically important. For example, if a probiotic intervention decreases the relative risk of disease X by 33%., this percentage sounds very impressive. However, if the baseline risk of contracting disease X is only 0.06% (e.g., it is a very rare condition), then the risk after the probiotic intervention is only 0.04% (still very rare, as reflected in the absolute risk reduction of 0.02%). Although the decrease of 33% that is reported as relative risk seems large, if you take into account the baseline risk, you realize that this is not clinically significant. The risk of 0.06% and 0.04% are essentially the same.

When evaluating an intervention, the context of the disease makes a difference. How often is this disease or condition occurring in the population being studied? The problem with reporting a relative risk reduction is that it is easy to overlook how common or uncommon the disease is to begin with.

Look for the “Number Needed to Treat”

One way to better assess the impact of an intervention is to calculate a “Number-Needed-to Treat” (NNT).  The NNT is the inverse of the absolute risk reduction.

From our example above, a 33% relative risk reduction of a condition with a prevalence of 0.06% (e.g., a very rare condition), means that the probiotic intervention had an absolute risk reduction of 0.02%. The NNT would be equal to 1/[0.0002]= 5000. This NNT of 5000 means that you’d need to treat 5000 patients with the probiotic intervention to change the outcome of only one patient.

Take a different scenario. If the disease was much more common (e.g, 9% prevalence) and the relative risk reduction was still 33%, then absolute risk reduction would be 3%. The NNT in this case would be equal to 1/(0.03)=33.3. This NNT of 33.3 means that you’d need to treat only 33 patients with the probiotic intervention to change the outcome of one patient. This treatment is much more likely to be meaningful in the population.

The NNT is a quick way for clinicians to evaluate an intervention to take into account the risk reduction in the context of the baseline risk.

Conclusion

When examining the results from clinical trials, just looking at percentage changes can be deceiving. Unfortunately, relative risk reduction often results in more sensational headlines, so beware of how the press, and even top quality journals, report study results. When assessing the clinical trial results in the context of clinical care, keep in mind how common or rare the disease is. Even a large percentage change may not make a big difference overall in patient outcomes if the initial risk was very low to begin with. Evaluate and interpret clinical trial results in their proper context.