PURPOSE OF THE STUDY.
To determine the usefulness of urinary bromotyrosine, a marker of eosinophil-catalyzed protein oxidation, in monitoring asthma control and predicting future exacerbations.
There were 57 people enrolled from the Cleveland Clinic with a diagnosis of asthma between the ages of 5 and 21 years. Recruitment occurred from July to September 2006 and follow-up from August to November 2006. All subjects were considered to be at baseline status and being seen as part of regularly scheduled visits. Those with other comorbid conditions were excluded.
Asthma Control Questionnaires (ACQ6) were used to assess asthma control given at the initial study encounter and at a 6-week follow-up. Spirometry was performed, and exhaled nitric oxide was measured. Spot clean catch urine samples were collected to determine free bromotyrosine levels by stable isotope dilution high-performance liquid chromatography with online mass spectrometry. Charts were reviewed for medical history, medication, and laboratory results.
Urinary bromotyrosine levels correlated significantly with indexes of ACQ6 at baseline and at follow-up. This correlation was not seen with respect to nitric oxide levels, spirometry, and blood metrics (immunoglobulin E, eosinophil count). Participants with higher baseline levels of urinary bromotyrosine were 18.1-fold more likely to have inadequately controlled asthma and fourfold more likely to have an asthma exacerbation during the study period.
Urinary bromotyrosine significantly correlates with measures of asthma control and is a good marker for predicting the risk of future asthma exacerbations in children.
Based on findings from this study, using urinary bromotyrosine levels as an objective marker for asthma control and in predicting risk for future exacerbations seems promising. However, the cost of such studies given its availability in select laboratories may be a limiting factor and deterrence in its widespread use, and confirmatory studies are needed.
- Copyright © 2012 by the American Academy of Pediatrics