New research shows that an immunoassay can detect a peptide in urine that is increased in children with sleep apnea. The test could provide a psychologically easier way to determine if a child has sleep apnea, an alternative to spending the night in a sleep clinic.
Sleep Review: Can you explain the highlights of your research and its findings?
Trevor Pitcher, PhD, Clinical Chemistry Fellow, University of Louisville: Somewhere around 2006, 2007, workers from the University of Louisville were looking at children who had sleep apnea and they compared their urine samples … and basically were trying to find a noninvasive test to diagnose sleep apnea. The primary way is overnight sleep studies, but they’re kind of limited because they’re expensive and time- and labor-intensive. So what they did is they analyzed the urine with mass spectrometry.
They were able to determine when you combine three markers together, it was very specific to obstructive sleep apnea.
Now we’re trying to develop a more commercialized detection for urocortin 3. What we want to do is develop, at least initially, a lab-developed test for urocortin 3. We had to start from scratch so what we did was worked to develop monoclonal antibodies, and antibodies that could detect the peptide in urine.
We’re working on getting the measuring range worked out. We’re still trying to lower the sensitivity because we’re trying to work out how low it [the threshold] needs to go.
SR: Did anything about your findings surprise you?
TP: Probably the thing that was most surprising was how difficult it was to get good quality antibodies for the peptide.
SR: Is testing for urocortin 3 something that can be done in a typical doctor’s office? Or will the urine need to be sent to either a standard urine-testing lab or to a more specialized lab?
TP: Probably to begin with, it would be something you’d send out somewhere. It would probably depend on when we’re able to do clinical trials and see how it works in real life. But maybe down the line it could be something you could do in more routine settings.
SR: When will clinical trials start?
TP: It may be possible to do it in the next year or two.
SR: Can the stress-coping peptide urocortin 3 be indicative of anything besides sleep apnea? If yes, how will a clinician determine if the peptide indicates sleep apnea or something else?
TP: That’s a really good question. That’s something that still needs to be worked out. I think it relates to the cardiovascular system, but offhand, I don’t know.
SR: What do you see as the barriers to a urine test for pediatric sleep apnea being implemented?
TP: I think, right now, the biggest barrier is working out what the actual concentration is in urine and working out the nuts and bolts of what detection level you need to be effective [in detecting sleep apnea]. Initial studies show it should be elevated.
SR: Who do you foresee as taking the urine sample—a pediatrician, a sleep specialist, etc?
TP: It would probably be initially a specialist in the beginning. I think what it comes down to is once we can get clinical trial data to see how it works out, it could be eventually used as more general screening and maybe then it could be from a pediatrician’s point of view.
SR: Can this urine test be used to detect sleep apnea in adults? Why or why not?
TP: At this point, I don’t know, since we haven’t done studies in adults. The challenging part with adults is there are a lot more confounding factors than in children. With adults, they may have hypertension or diabetes or cardiovascular conditions that may affect the test. It may be elevated and they might have no actual sleep apnea, so it may be a little easier to work out in children first.
SR: How would treatment be different for children?
TP: I think typically it depends; the challenge is that there are a lot of things that cause SA so it depends on the actual cause. It really depends on the cause.
The study has not yet been published, but those interested in reading more can get additional information here.
A.J. Zak is an associate editor for Sleep Review. Email questions and comments to email@example.com.