Can Microbiome Diagnostics Be Standardized Across Populations?

The human gut microbiota is remarkably diverse. Diet, lifestyle, medication, genetics, age, and environmental factors all influence the composition of our gut microbiome, meaning that even healthy individuals from different parts of the world can have very different microbial profiles.

This natural variation has long presented one of the biggest challenges in microbiome diagnostics: can a diagnostic test developed using one reference population provide reliable results when applied elsewhere?

The question is more than academic. For microbiome testing to become part of routine clinical practice, diagnostic results must be consistent—not only across laboratories and operators, but also across different patient populations. If geographical differences systematically affect test performance, widespread clinical implementation becomes difficult.

A newly published peer-reviewed study in Gut Microbes provides encouraging evidence that this challenge can be addressed through a standardized diagnostic approach.

Why geographical variation matters in microbiome diagnostics

Unlike many conventional biomarkers, the gut microbiome exhibits large variation between individuals and populations due to differences in diet, lifestyle, environmental exposures, and host characteristics. As a result, microbiome profiles differ substantially between individuals, populations, and countries.

These differences have made it difficult to establish standardized diagnostic frameworks. Traditional sequencing approaches often generate data on thousands of microbial taxa, many of which naturally fluctuate between healthy individuals. While this provides valuable biological insight, it also introduces analytical complexity and raises questions about reproducibility across independent studies and patient populations.

For years, researchers have debated whether microbiome diagnostics require population-specific reference ranges or whether standardized approaches can be applied globally.

A different approach to microbiome diagnostics

Rather than attempting to define a "healthy microbiome" based on the abundance of hundreds or thousands of bacterial species, an alternative strategy is to evaluate overall deviation from a validated healthy reference state using a predefined panel of clinically relevant microbial markers and a standardized interpretation algorithm.

This principle forms the basis of the GA-map® Dysbiosis Test.

Instead of recreating every aspect of an individual's microbiome, the test focuses on microbial patterns associated with gut microbiota imbalance (dysbiosis). A validated mathematical algorithm integrates information from a panel of predefined bacterial markers into the Dysbiosis Index (DI), providing a standardized assessment of microbiome status.

The critical question addressed by the new study was whether this standardized framework would remain reliable when applied outside the Scandinavian population on which it was originally developed.

Evaluating diagnostic performance across multiple countries

To investigate this question, researchers analyzed more than 800 stool samples collected from healthy and non-healthy individuals across several countries, including:

• Norway
• Sweden
• Germany
• Italy
• United Kingdom
• United States
• Canada

Each sample was analysed using the same standardized GA-map® Dysbiosis Test and interpretation algorithm. The objective was straightforward: determine whether geographical differences in microbiota composition would influence dysbiosis classification.

Key findings

Healthy individuals showed consistent Dysbiosis Index values

Despite known differences in gut microbiota composition between countries, healthy individuals demonstrated remarkably similar Dysbiosis Index distributions.

Importantly, no non-Scandinavian population exhibited a systematic increase in dysbiosis classifications simply because of geographical origin. This suggests that geographical variation alone does not compromise standardized microbiome assessment when using a predefined diagnostic framework.

Healthy and non-healthy populations remained clearly distinguishable

Across all participating countries, non-healthy cohorts consistently showed higher Dysbiosis Index values than healthy controls.

This demonstrates that the diagnostic framework retained its ability to distinguish microbiome imbalance across geographically diverse populations, supporting the robustness and transferability of the standardized approach.

Why these findings matter

Historically, microbiome diagnostics have often been viewed as inherently population-specific because healthy microbial composition differs considerably between regions.

The findings from this study suggest a different perspective.

Rather than requiring identical microbiota compositions across countries, standardized diagnostics can focus on identifying deviations from a validated normobiotic reference state. This allows clinically meaningful interpretation while accommodating the natural biological variation that exists between populations.

As microbiome testing continues to evolve from research applications toward routine clinical use, reproducibility and standardization will become increasingly important. Diagnostic solutions must deliver consistent results regardless of where samples are collected or analysed, enabling laboratories and clinicians to make reliable, evidence-based decisions.

Looking ahead

The publication Towards Standardized Gut Microbiota Diagnostics: Normobiosis Beyond Geographical Borders contributes important evidence to an ongoing discussion within the microbiome field.

While further research across additional populations and clinical applications will continue to strengthen our understanding, these results demonstrate that standardized microbiome diagnostics can be both scientifically robust and geographically transferable.

For laboratories, clinicians and researchers working to integrate microbiome analysis into routine healthcare, this represents an encouraging step toward more reproducible, scalable and clinically meaningful microbiome testing.

Read the full publication

Hiseni P. et al. Towards Standardized Gut Microbiota Diagnostics: Normobiosis Beyond Geographical Borders. Gut Microbes (2026).

Read the full peer-reviewed publication here:
https://www.tandfonline.com/doi/full/10.1080/19490976.2026.2701485