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Urinary 3-bromotyrosine (uBrTyr) levels cannot be used as a single parameter to diagnose aspirin-exacerbated respiratory disease (AERD), according to a study published in Respiratory Research. Urinary BrTyr levels are elevated and indistinguishable both in patients with AERD and patients with aspirin-tolerant asthma (ATA) compared with healthy controls.
Participants in the study included patients with AERD (n=240), patients with ATA (n=226), and healthy controls (n=71). Forced expiratory volume in 1 second (FEV1) and FEV1/forced vital capacity (FVC) values were calculated with the use of spirometry at baseline and after administration of 4 puffs of salbutamol. Blood eosinophil levels were calculated with a Fuchs-Rosenthal chamber. Researchers used morning urine samples to measure urine creatinine using automated chemical analyzer COBAS Integra 400 plus (Roche Diagnostics USA). Urinary BrTyr was assayed using stabled isotope dilatation High Performance Liquid Chromatography. Urinary leukotriene E4 (uLTE4) was measured by direct enzyme immunoassay; results of these measurements were expressed in pictograms/mg of creatinine.
The AERD and ATA groups had levels of uBrTyr, uLTE4 levels, and blood eosinophils that were significantly higher than the control group. Urinary BrTyr levels were not significantly different between AERD and ATA (P =.3406), but uLTE4 levels and blood eosinophils were significantly higher in AERD (P <.0001) compared with ATA (P =.004). In both phenotypes, uBrTyr and uLTE4 levels correlated significantly with each other (AERD: R=0.160; P =.01; ATA: R=0.151; P =.02). Blood eosinophils also correlated significantly with uLTE4 levels in ATA (R=0.165; P =.01) and AERD (R=0.276; P <.0001), but no such correlation was found between eosinophil counts and uBrTyr levels. Neither uBrTyr nor uLTE4 levels correlated with severity of airway obstruction in either asthma phenotype. Only a borderline correlation was found between FEV1/FVC and uLTE4 in ATA (R=0.140; P =.05).
With regard to using increased uBrTyr levels as a biomarker of asthma in adult populations, this study confirms previous findings, but elevated uBrTyr levels alone cannot differentiate between patients with AERD and patients with ATA.
Disclosures: One author acknowledges competing interests; please see reference for a full list of author disclosures.
Reference
Comhair SAA, Bochenek G, Baicker-Mckee S, et al. The utility of biomarkers in diagnosis of aspirin exacerbated respiratory disease. Respir Res. 2018;19:210.
