SCIENTISTS are warning that advanced technologies that read long strings of DNA can return false data that could falsely indicate that someone has a genetic difference that heightens their risk of a particular disease.

The new methods which can read lengthy sections of genetic material – categorised by a series of letters – are up to 99.8% accurate, but in a genome of more than three billion characters, they said this may equate to millions of mistakes in the results.

Researchers at the University of Edinburgh’s world-renowned Roslin Institute say data produced by these technologies should be interpreted with caution, as it may create problems for analysing genetic information from people and animals.

Older genetic sequencing technologies were focused on reading short strings of DNA, which would then be patched together in a process that is time consuming and labour intensive.

This approach is said to be useful for reading individual genes but is inappropriate for entire organisms.

The team examined three recent studies reporting human genome sequences from long-read technologies.

That data contained thousands of errors even after corrective software was used, they found. Such mistakes could have major implications if these technologies are used in clinical studies to diagnose patients, the team suggests.

The Roslin Institute receives strategic funding from the Biotechnology and Biological Sciences Research Council (BBSRC), and the team’s finding are reported in the scientific journal Nature Biotechnology.

Professor Mick Watson, of the Roslin Institute, said: “Long-read technologies are incredibly powerful but it is clear that we can’t rely on software tools to correct errors in the data – some hands-on expertise may still be required.

“This is important as we increasingly use genomic technologies to understand the world around us.”

He said there were also implications for people who wanted to find out more about their ancestry and were using commercial DNA testing.

“Whilst we do not test this in the research, I would recommend that anyone be very careful when interpreting personal genome data from one of the long-read technologies either in the context of ancestry or genetic health.

“However, the current tools used by, for example and, tend to be either chip based, or short-read sequencing.

“Whilst both of these have the capacity for errors, they do not have anywhere near as high an error rate as the long read technologies.”

As commercial DNA testing gains popularity, it can uncover surprises, as Rondel Holder told The New York Times.

He had always thought of himself as a New Yorker, from Brooklyn, with Grenadian and Jamaican roots, but his DNA test results debunked that theory, revealing that much of his ethnicity could be traced to two African countries – Togo and Benin.

Watson cautioned: “Personally speaking I would recommend everyone takes consumer genetic testing … with a pinch of salt.”