By ANDREW POLLACK
New York Times
Want to know how long you will live?
Blood tests that seek to tell people their biological age - possibly offering a clue to their longevity or how healthy they will remain - are now going on sale.
But contrary to recent media reports, the tests cannot specify how many months or years someone can expect to live. Some experts say the tests will not provide any useful information.
The tests measure telomeres, which are structures on the tips of chromosomes that shorten as people age. Various studies have shown that people with shorter telomeres in their white blood cells are more likely to develop illnesses like cancer, heart disease and Alzheimer's disease, or even to die earlier. Studies in mice have suggested that extending telomeres lengthens lives.
Seizing on that, laboratories are beginning to offer tests of telomere length, setting off a new debate over what genetic tests should be offered to the public and what the ethical implications would be if the results were used by employers or others.
Some of the laboratories offering the tests emphasize that the results are merely intended to raise a warning flag.
"We see it as a kind of wakeup call for the patient and the clinician to say, 'You know, you're on a rapidly aging path,'" said Otto Schaefer, vice president for sales and marketing at SpectraCell Laboratories in Houston, which offers a test for $290.
Another company, Telome Health of Menlo Park, Calif., plans to begin offering a test later this year for about $200. It was co-founded by Elizabeth H. Blackburn of the University of California at San Francisco, who shared a Nobel Prize in 2009 for discoveries related to telomeres.
Calvin B. Harley, the chief scientific officer at Telome Health, said the test would be akin to a car's dashboard signal, a "check engine light." He compared it to a cholesterol test, but more versatile since it can predict a risk of various illnesses, not just heart attacks.
But among the critics of such tests is Carol Greider, a molecular biologist at Johns Hopkins University, who was a co-winner of the Nobel Prize with Blackburn.
Greider acknowledged that solid evidence showed that the 1 percent of people with the shortest telomeres were at an increased risk of certain diseases, particularly bone marrow failure and pulmonary fibrosis, a fatal scarring of the lungs. But outside of that 1 percent, she said, "the science really isn't there to tell us what the consequences are of your telomere length."
Recent media reports speculated on the tests and their possible implications, including ethical problems.
"You could imagine insurance companies wanting this knowledge to set rates or deny coverage," said Dr. Jerry W. Shay, a professor of cell biology at the University of Texas Southwestern Medical Center in Dallas, who is an adviser to Life Length.
Test vendors say the speculation is running wild.
"It doesn't mean we will tell anyone how long they will live," said Maria Blasco, a co-founder of Life Length and a molecular biologist at the Spanish National Cancer Research Center in Madrid. Even if a 50-year-old has the telomere length more typical of a 70-year-old, she said, "this doesn't mean your whole body is like a 70-year-old person's body."
Still, she said, "We think it can be helpful to people who are especially keen on knowing how healthy they are."