Spanish scientists have invented a blood test they say can tell you how much longer you have to live.Life Length, the company behind the project, claims that the test will give people an idea of the speed at which they are ageing, and a general assessment about their state of health.The 435-euro ($700) test, which will be available in Europe at the end of the year, measures the length of telomeres on a person's chromosomes, which are thought to be linked to longevity.The test looks for high concentrations of short telomeres, which correlate with an increase in your biological age.Colin Blakemore, professor of Neurobiology at Oxford University, said the test looked at "biological age", rather than chronological age, or the time since a person was born.Short on science?The test measures the length of telomeres on DNA in white blood cells in the plasma.White blood cells are involved in immune defence, and increased production during sickness may skew the reading of the test.The test also fails to look at other measures that can indicate the overall health of a person."[It] won't even measure reliably the true telomere length [of cells] of the tissue of the body," said Blakemore.Critics also claim the test may lead to healthcare discrimination and apprehension about a person's health."I'm not convinced of it's reliability or ethical implications," he added.Source: Aljazeera