If a genetic test report comes back with a “variant of uncertain significance,” it is easy to read that as bad news. In practice it means something narrower and far less alarming: the laboratory found a spelling change in a gene but does not yet have enough evidence to say whether it affects health. This explainer walks through what that classification is, why it happens so often, and what tends to happen next.
The five-tier system behind the label
Most clinical laboratories classify variants using a framework published by the American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology in 2015. It sorts each variant into one of five tiers:
- Pathogenic — strong evidence the variant causes disease
- Likely pathogenic — probably disease-causing
- Uncertain significance (VUS) — evidence is insufficient or conflicting
- Likely benign — probably harmless
- Benign — strong evidence it is harmless
The framework combines up to 28 lines of evidence — population frequency, computational predictions, laboratory functional studies, how the variant tracks with disease through a family, and more. Each piece is weighted (very strong, strong, moderate, or supporting). A variant lands in the middle uncertain tier whenever the criteria for both ends are unmet, or when the evidence pulls in opposite directions. A VUS is therefore a statement about the data, not a verdict on your health.
Why uncertain results are so common
VUS findings are largely a side effect of how much we now sequence. Testing a single gene such as BRCA1 rarely produces one; testing a large multigene panel often does, because every additional gene adds chances to encounter a rare, never-before-catalogued change. In one cohort selected for high hereditary-cancer risk, the overall VUS rate reached roughly 46% on the broadest panels.
There is also a well-documented equity problem. Reference databases were built mostly from people of European ancestry, so variants seen in under-represented populations are more often unfamiliar and harder to interpret. Individuals of Asian or Middle Eastern ancestry have been reported to receive a VUS roughly 33–35% of the time, versus about 17–20% for those of Ashkenazi Jewish or European ancestry. The variant is not more dangerous in these groups — there is simply less data to compare it against.
What a VUS does and does not change
Guidelines from the National Comprehensive Cancer Network are explicit on this point: a VUS should not be acted on as though it were pathogenic. Clinical decisions — screening intervals, risk-reducing surgery, who else in the family to test — are based on personal and family history, not on an uncertain variant. Equally, relatives are not routinely tested for a VUS, because its meaning is unknown.
| Classification | Typical clinical use |
|---|---|
| Pathogenic / Likely pathogenic | May drive screening, prevention, and cascade family testing |
| Uncertain significance (VUS) | Managed by family history; not used to change care |
| Benign / Likely benign | Considered a normal finding |
Uncertainty is usually temporary
The reassuring pattern in the long-term data is that most VUS findings are eventually resolved downward. In a large review of BRCA1 and BRCA2 variants, the large majority of reclassified VUS were moved to benign or likely benign — one analysis found about 92% of reclassified VUS were downgraded, and only a small minority were upgraded toward pathogenic. As databases grow and families are followed over years, the evidence usually accumulates on the harmless side. This is why laboratories may re-issue a report, and why staying connected to a clinic matters more than acting immediately.
This pattern echoes the work of long-running hereditary-cancer registries such as the PROMPT registry, which pooled patient-reported variants in genes like BRCA1, BRCA2, CHEK2, and ATM precisely to study how uncertain results behave over time — research cited across the oncology literature, including ASCO’s Journal of Clinical Oncology.
The bottom line
A variant of uncertain significance means the science is still in progress for that specific change — not that you carry a known risk. It rarely alters medical care on its own, it is more common simply because we sequence more and our reference data is uneven, and it usually gets resolved toward benign as evidence grows. The practical step is to keep the report, note the variant identifier (such as an rs80357906-style reference), and ask your clinic whether reclassification updates are available later.
Educational explainer, not medical advice. For your own testing or results, speak with a clinician or genetic counsellor.