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Hope for the Future
New Study Shows Promise of Non-invasive Measures for Thalassemia and Sickle Cell Disease

CHORI clinical scientists Ellen James, MD, Elliot Vichinsky, MD, and their colleagues have just published a new study highlighting the potential for using carbon monoxide measurements as an alternative to blood testing in patients with sickle cell disease (SCD) or thalassemia, blood disorders that affect thousands of people in the United States, and millions across the globe.

“Normally we think of measuring different parameters in blood to see what is going on or whether transfusion is necessary, but measuring carbon monoxide is another way to determine how much you are breaking down hemoglobin, and the nice thing is that you can measure it without sticking anyone with a needle,” explains Dr. James.

“The nice thing about measuring carbon monoxide is that you can do it without sticking anyone with a needle .”

The concentration of carbon monoxide (CO), a byproduct of red blood cell breakdown, can be measured in the breath. As red blood cell breakdown is significantly increased in patients with blood disorders, the thought was that increased CO levels in the breath could be a potential indicator of either disease in undiagnosed newborns, or of the need for transfusions in current patients. The study, published in Pediatric Hematology and Oncology, assessed the utility of CO measurements in both cases.

“California already does newborn screening for SCD and thalassemia, but a number of states don’t. We wanted to find out if CO testing was a way to do state-wide screening for these disorders both inexpensively and non-invasively,” says Dr. James.

The results indicate that carbon CO levels are indeed predictive of hemoglobin disorders when comparing healthy controls to patients with SCD or thalassemia. Both the positive predictive value – which patients had thalassemia or SCD, and the negative predictive value – which patients didn’t have these disorders, were high – 93 and 94 percent respectively.
“It turns out that carbon monoxide testing is a really useful tool to screen out kids with blood disorders. The problem, though, is that you can still have false positives.”
“If someone has an infection or if they have certain nutritional deficiencies, for example, that would come out as a positive in CO testing," says Dr. James.

“This means that although you can't yet use CO testing alone, it does, however, give you a smaller pool of kids that require blood testing to confirm disease.”

As a result, this technique could be particularly useful in states without current screening measures, as well as in other countries in which CO testing could be more easily implemented than the traditional hemoglobin testing requiring a blood draw. The sooner patients are diagnosed with these potentially life-threatening disorders, the sooner they can receive treatment, and the better their chances are for long-term survival.
The second part of the study looked at whether or not CO measurements could be used to indicate the appropriate timing for blood transfusions in patients with SCD or thalassemia.

“We wanted to see if we could use CO measurements as a way to determine whether a patient was ready for a transfusion or not,” says Dr. James. “Normally we have to do a blood test with a needle stick, so we wanted to see if we couldn’t use CO measurements instead.”

Unfortunately, the results for this portion of the study were less conclusive due to the small number of patients who were able to be studied over time, as needed to evaluate the use of CO measurements for transfusion timing. The preliminary results, however, do suggest that there is value to further research.

“You might still need a blood test, but you could potentially do them less frequently,” says Dr. James. “Any reduction in needle sticks is of definite benefit.”

Future studies will need to focus on a larger sample size to determine how effective CO measurements could be in reducing the need for needle sticks in the ongoing management of patients with these blood disorders. In the mean time however, there is hope for CO measurement becoming a more cost effective and less invasive approach in both the diagnosis and management of these disorders.

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Tuesday, May 17, 2011 8:49 AM

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