Dec. 1, 2010 -- A new DNA test is accurate at predicting which children are least likely to have their scoliosis -- an abnormal curvature of the spine -- progress to a severe curvature, according to new research.
Doing so can save medical expenses as well as unneeded X-rays and time off work for parents, says researcher Kenneth Ward, MD, chief scientific officer of Axial Biotech Inc., in Salt Lake City, which developed the test.
X-rays can quantify the current degree of curvature, but predicting which curvature will progress isn't always easily done, Ward says.
''This test is the first to start to give that reassurance of who is at low risk," he tells WebMD.
The research is published online in the journal Spine.
Scoliosis: Predicting Progression
Scoliosis affects up to 4% of teens, Ward writes.
If the curvature progresses too much, the first step is often spinal bracing, needed by up to 10% of people with the condition.
If the curvature continues to worsen, spinal fusion is often recommended.
Scoliosis: The Test
Ward and his colleagues evaluated 697 patients, aged 9 to 13, who had mild, moderate, or severe scoliosis.
Of the 697:
- 277 were low-risk girls, representing a group that was screened
- 257 were higher-risk girls, being followed at referral centers
- 163 were high-risk boys
The researchers obtained saliva samples and analyzed the DNA.
The test evaluates 53 genetic markers that are associated with scoliosis progression. It takes into account the patient's current spinal curvature, what doctors call the Cobb angle. (When the Cobb angle is greater than 45 degrees, the scoliosis is considered severe.)
''We do a test for each of these 53 markers," Ward says. He compares these 53 markers to 53 ''high-risk cards" dealt by one's genetics. "Severe forms of scoliosis are quite genetic," he says.
The analysis produces a score between 1 and 200. "The higher the score, the more 'bad cards' the child was dealt," he says.
The score represents a patient's risk for developing a severe spinal curve.
A score or 50 or lower is low risk, 51 to 180 intermediate, and 181 to 200 high risk.
Ward found that the test, called Scoliscore, has a 99% accuracy rate in identifying low-risk patients -- those least likely to progress to a curvature of 40 degrees or more.
''For the low-risk patients, it predicts less than a one in 200 chance they will end up progressing to need surgery," he says. That's overall for the low-risk group, he says; the lower the score in that low-risk category, the lower the chances.
Scoliosis Progression Test: Practical Points
The test isn't a screening test, Ward tells WebMD, but a way to predict which children who already have scoliosis are at low risk of progressing to severe curvatures.
For those who are found to be at low risk, he says, experts would typically advise less intense follow-up, ''maybe once a year." They probably wouldn't need as many X-rays as those with a higher score, he says.
The intermediate-risk group needs specialist care, as does the high-risk group, and more intensive follow-up, he says.
The test can only be used in white patients, Ward says, as that is the only ethnic group with enough affected children to measure the test's accuracy, despite the researchers' efforts to recruit other ethnic groups for testing.
If patients pay totally out of pocket, the test is expensive -- about $2,950, Ward says. But he says for patients with insurance, the out-of-pocket cost is typically $20 or less. And for indigent patients, the test can be obtained for free, he says.
The test is regulated under the federal Clinical Laboratory Improvement Amendments and doesn't require premarketing clearance by the FDA.
Ward says about 450 centers offer the test.
Scoliosis Test Not Perfect
Jeffrey Neustadt, MD, a Tampa Bay, Fla., orthopedic surgeon and affiliate associate professor of orthopedic surgery at the University of South Florida in Tampa, sees pros and cons to the new test.
"It's really exciting work," he tells WebMD. But, he adds, "It's very expensive. Even if it's covered by insurance, it's still an expense."
Like most tests, it's not perfect. "If you are one of those patients with a low number, you can be pretty confident that it is not going to progress, but you can't be 100% sure of that."
Neustadt says the most difficult case to predict is an immature patient with an intermediate-degree curve. "Fortunately, there are not that many [who fit that description]," he says.