New Technique for Diagnosing Hemophilia
LONDON (AP) _ A new, rapid method for examining the gene linked to the most common form of hemophilia will identify people with the genetic defect more accurately than before, British researchers reported in last week’s Lancet.
The new technique will detect ″virtually 100 percent of carriers″ of hemophilia A, according to the doctor who developed the technique, Francesco Giannelli of Guy’s Hospital in London.
The medical director of the National Hemophilia Foundation in the United States said the report is an ″exciting″ development, though it was based on work with only two patients.
About 20,000 American men have hemophilia, a deficiency or absence of one of the proteins needed to clot blood, said a National Hemophilia Foundation spokesperson.
Hemophilia A, caused by a defect in the protein Factor VIII, is the most common form, affecting 85 percent of the cases.
Women carry the defective gene but don’t suffer any symptoms. Men can inherit any one of a number of potential defects on this large gene.
Dr. Jean Lusher, the director of the National Hemophilia Foundation, said the British technique is a ″new version of examining genes that’s easier and quicker to do, and will help many families.″
She said it will be particularly important for hemophiliacs’ female relatives who might want children. There’s a 50 percent chance the child of a carrier will inherit the defective gene.
Currently, Giannelli said, doctors searching for hemophilia look at specific regions known to be important. But, ″only a very small proportion of mutations could be identified,″ and only half of the carriers were detected, he added. The new test takes a more thorough look at the gene.
Though he reported on only two patients, Giannelli said it is the technique that is significant, not the number of patients.
Lusher was not put off by the small sample. She says the technique described is ″superior to anything I’ve seen,″ and she suspects it would work on all people.
″I thought the beauty of this is that they have applied a highly sophisticated, new technique to rapidly scan the entire gene, not just a segment of it,″ said Lusher, who is also the director of hematology-oncology at the Children’s Hospital of Michigan.
Currently, Lusher explained, when one mutation is detected, doctors look for a similar defect in female relatives. The problem is there may be more than one mutation on the gene. Some women may harbor other genetic defects not originally spotted. So a carrier of hemophilia would go undetected, she added.
″This advance is substantial for at least three reasons,″ Giannelli wrote in The Lancet.
Direct diagnosis is more precise and potentially cheaper than gene tracking based on fragments; it should increase the proportion of families helped to virtually 100 percent; and it provides vital information about the molecular biology of hemophilia.
″In families where it’s been difficult to say whether the women are carriers, this seems to hold real promise,″ Lusher said. ″There’s an enormous amount of individuals who fall into that category.″