A Mayo Clinic study has shown that whole-exome sequencing (WES) – where a person’s entire DNA sequence is determined using a section of the genome – is an effective step in treating patients who have spent years waiting on a diagnosis, leading the Mayo Individualized Medicine Clinic’s director to predict the process will in the future be routinely performed on newborn babies.

The director, Dr Konstantinos Lazaridis, also led the study, which looked at how effective WES was in diagnosing patients on a “diagnostic odyssey”, where they had seen multiple healthcare providers over a significant period, without receiving a diagnosis. In the study, almost a third of patients were diagnosed successfully as a result of WES.

“With several million patients in the US suffering from a rare or an undiagnosed disease, WES is emerging as a promising, affordable test that could enhance clinical care by improving diagnosis of such patients,” said Lazaridis. “I envision one day WES will be performed on every newborn and every patient who needs medical care.”

WES currently costs around $8,000 in the US per patient, dramatically less than whole-genome sequencing, but is expected to drop further in cost as sequencing becomes cheaper and easier to achieve.

However, despite its relatively high present cost, the Mayo Clinic found that WES was currently a worthwhile diagnostic tool for the long-term undiagnosed, as it would unearth rare genetic conditions that would otherwise be exceptionally difficult to identify.

“The significant diagnostic yield, moderate cost and notable health marketplace acceptance of whole-exome sequencing for clinical purposes, compared with conventional genetic testing, make it a rational diagnostic approach for patients on a diagnostic odyssey,” added Lazaridis.

In the study, 51 patients submitted samples for sequencing with WES, 29% of who were diagnosed as a result.

“The success rate of 29 percent, which is about twofold higher of conventional genetic evaluations for such patients, makes WES a reasonable diagnostic approach for patients on a diagnostic odyssey,” he said.

In the US, WES is already starting to be used to diagnose patients, although the current price is not always accepted.

In Mayo Clinic study, 27% of patients were supported for WES by Medicaid, and 38% were either partially or completely covered by their insurance. Only 15% of cases were denied by their insurance providers, a rate considered low for this type of testing in the US.

In time, however, this is likely to decrease further, as the cost of WES drops from the thousands into the hundreds. And if Lazaridis is to be believed, there will come a time where using WES to sequence a baby’s DNA will be as standard as determining its blood type.