"Our findings really shake the boat of conventional thinking about hemochromatosis, and are understandably disturbing to self-help groups pushing for universal genetic, as opposed to biochemical, screening," says Vincent J. Felitti, recently retired chief of preventive medicine at Kaiser Permanente in San Diego and co-director of the investigation. And the fate of the HH gene test may influence implementation of other genetic tests.
The problem for HH is statistical: Most people who have the clinical disease have mutations in the HFE gene, but most people who have those mutations never develop the symptoms. In genetic lingo, a mutation is incompletely penetrant if not everyone who inherits it actually develops the associated trait or illness. Screening for an incompletely penetrant mutation can lead to predictions that do not come to pass. "Before you can really make a cost/benefit assessment for a genetic test, you have to know the penetrance of the ...
