Functional studies that support reclassification of a variant of uncertain significance (VUS) primarily demonstrate what?

• A. Demonstrate the functional impact of the variant on the gene or protein.
• B. Determine the inheritance pattern in the family.
• C. Assess the patient’s psychosocial impact.
• D. Provide cost-effectiveness of testing.

Answer: (A)

The main idea is that reclassifying a variant of uncertain significance relies on direct evidence of how the variant changes biology. Functional studies test whether the variant alters the gene product’s function—such as changes in enzymatic activity, protein stability, proper splicing, cellular localization, or interactions with other molecules. If these studies show that the variant disrupts normal function in a way consistent with disease, that functional impact supports moving the variant toward likely pathogenic. If they show normal function, that supports a likely benign classification. This focus on the molecular effect is what makes functional studies the key evidence for reclassification.

In contrast, determining inheritance patterns in the family depends on how the variant segregates with disease in relatives and doesn’t directly prove how the variant affects the gene product. Assessing the patient’s psychosocial impact is about experience and counseling needs, not biology. Providing cost-effectiveness relates to health economics, not molecular consequences.