Tag Archives: testing

Should You Do a Gut Microbiome Test? No — Here’s Why

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J McCreary. MedPage Today; 2/26/26. Open Access! Same Stool Sample, Different Results in Gut Microbiome Tests

An excerpt:

“Direct-to-consumer gut microbiome tests produced markedly different results — even when analyzing the same stool sample, researchers found.

Identical fecal samples sent via 21 home-testing kits to seven anonymized direct-to-consumer testing companies yielded a wide variation in reported bacterial abundance and in the health assessments generated from those data, reported Stephanie L. Servetas, PhD, of the National Institute of Standards and Technology (NIST) in Gaithersburg, Maryland, and colleagues in Communications Biology.

In some cases, there was not even agreement among kits produced by the same company…

When researchers compared 18 commonly reported microbial genera across companies, no single provider aligned with the consensus profile for all 18. Across the full dataset, 1,208 unique taxa were reported, but only three genera appeared in every company’s results…

The authors said the discrepancies likely stem from differences in sample processing, sequencing methods, bioinformatics pipelines, reference databases, reporting thresholds, and quality control standards…

“These tests have become popular, partly because people, I think, are increasingly interested in health and wellness, and partly because the gut microbiome has been linked — at least in the public imagination — to the idea that you can improve a whole range of conditions through diet and lifestyle changes,” said co-author Diane Hoffmann, MS, JD, of the University of Maryland in Baltimore.

“There’s been a lot of hype around that, but the hype doesn’t really match the evidence. These tests often have limited evidence behind them, especially when it comes to informing clinical decisions or even basic dietary recommendations,” she added. “So the marketing can be questionable, and consumers can end up misinterpreting or over-trusting results that aren’t very reliable.”

Related article from Houston Methodist Hospital (2024): Should You Do a Gut Microbiome Test? Key point: “While these tests seem to be effective in mapping the gut microbiome, there is currently no benchmark for what a ‘normal’ gut microbiome looks like. So the question becomes what to do with the results…microbiomes are highly variable — even normal, healthy ones. This makes it incredibly challenging to define the patterns or signatures that suggest a microbiome has become imbalanced. Plus, the at-home steps for correcting microbiome imbalance aren’t established either.”

My take: It is uncomfortable informing families that these gut microbiome tests have little clinical value because there is not a proper way to interpret the results. In addition, this study shows that the tests from one place to another produce wildly different results.

While one’s microbiome is important, we still don’t understand what exactly is a normal microbiome.

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Highway to El Chalten and Mount Fitz Roy, Argentina

Impact of Testing (or No Testing) for Rumination Syndrome Outcomes

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JS Khoo et al. J Pediatr Gastroenterol Nutr. 2025;80:611–616. Impact of diagnostic testing on outcomes of children with rumination syndrome

Background: “A prior study from our institution showed that many patients undergo extensive diagnostic testing, which is associated with high financial cost with low clinical yield and delay in diagnosis.”

Methods: This was a retrospective study with 152 children (60% female, median age of diagnosis 13 years) with rumination syndrome (RS). 22 patients (14%) had diagnostic testing that confirmed RS.

Key findings:

  • The confirmatory testing group was more likely to need supplemental nutrition (p ≤ 0.001) and to receive intensive treatment (68% vs 24%) (p < 0.001)
  • After treatment, the proportion of patients without vomiting increased in both groups without a statistically significant difference between the two groups or needing supplemental nutrition.

Discussion Points:

“Our findings reveal that despite advancements in testing methodologies, undergoing diagnostic testing and receiving a positive result for RS is not associated with improved outcomes, specifically in cessation of vomiting, after treatment. In situations where patients and caregivers have difficulty accepting the clinical diagnosis, selective testing may be justified as acceptance of the diagnosis is a crucial aspect of the therapeutic plan for all gut-brain interaction disorders.”

Limitations included selection bias. While there were not overt differences in outcomes, the confirmatory testing group required more intensive treatment. As such, the testing may have some benefit in this group (though this was not identified in this retrospective study).

My take (borrowed in part from the authors): “We recommend that clinicians avoid diagnostic testing in children who clearly meet symptom-based criteria for RS and accept the diagnosis.”

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Train bridge near Chickamauga dam (Tennessee River).
There is a blue heron about to take flight due to the oncoming train

When We Can Stop Pre-Procedure Screening For COVID-19

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Briefly noted: S Sultan, SM Siddique et al. Gastroenterol 2020; 159: 1935-1948. Full text: AGA Institute Rapid Review and Recommendations on the Role of Pre-Procedure SARS-CoV-2 Testing and Endoscopy

Table 1 provides a summary of the recommendations and indicates a threshold for which routine pre-procedure testing may not be needed:

  • “For endoscopy centers where the prevalence of asymptomatic SARS-CoV-2 infection is low (<0.5%), the AGA suggests against implementing a pretesting strategy.”
  • Conditional recommendation, very low certainty evidence
  • Rationale: “In low-prevalence settings, a pretesting strategy may not be informative for triage due to the high number of false positives, thus PPE availability may drive decision-making.”

My take: Particularly after the rollout of vaccination to health care providers, routine testing for SARS-CoV-2 is not likely to be needed once the prevalence drops to low levels.

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COVID-19 -New Infection Fatality Data & How to Fix the Testing Mess

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From Annals of Internal Medicine 2020 https://doi.org/10.7326/M20-5352: J Blackburn et al. Full Text: Infection Fatality Ratios for COVID-19 Among Noninstitutionalized Persons 12 and Older: Results of a Random-Sample Prevalence Study

Background: Mortality rates have been calculated from confirmed cases, which overestimates the infection fatality ratio (IFR). To calculate a true IFR, population prevalence data are needed from large geographic areas where reliable death data also exist.

Results: The Table below suggests IFR of 0.01% for those <40, 0.12% for those 40-59, and 1.71% for those ≥60 in noninstitutionalized persons.  The Table indicates nearly a 3-fold increase risk in Non-White persons. Whites had an IFR of 0.18%; non-Whites had an IFR of 0.59%. Also, I think the Table incorrectly suggests that Females have a higher IFR than Males (but the numbers suggest that they are equivalent).

From The New Yorker, Atul Gawande: We Can Solve the Coronavirus-Test Mess Now—If We Want To

This is a lengthy article which describes some of the mistakes that we’ve made with testing, some of the technical details with various tests, pooled testing, at-home testing, wastewater testing, and how to fix testing (including assurance testing) to gain control of this pandemic.

An excerpt:

We could have the testing capacity we need within weeks. The reason we don’t is not simply that our national leadership is unfit but also that our health-care system is dysfunctional….

In the United States, getting a test is anything but easy…[And] through early August, results routinely took four days or more, making the tests essentially useless. 

“Assurance testing” has been required by countries such as Iceland, France, and Germany for travellers from abroad in order to avoid a mandatory two-week quarantine