Published Online: April 12, 2016
Leukotrienes are small endogenous chemicals thought to play an important role in inflammatory disease states. LTE4 is a stable end-product of the leukotriene pathway and can be measured in urine. The significance of measuring this metabolite in diseases such as asthma, and aspirin exacerbated respiratory disease (AERD) etc. has been shown in prior experimental conditions. However, the value of this test in a ‘real-world’ scenario using a commercially available assay in an outpatient setting is not clearly known.
In this study published in The Journal of Allergy and Clinical Immunology: In Practice, Divekar and colleagues conducted a retrospective analysis of patients who underwent measurement of urinary LTE4. Patients with physician assigned respiratory diagnoses of asthma, allergic rhinitis, chronic rhinosinusitis with polyps; chronic rhinosinusitis without polyps and aspirin sensitivity were included for analysis. The controls included those without the diagnoses of interest who underwent LTE4 measurement for evaluation of possible systemic mastocytosis or mast cell activation disorders. but after work up no specific cause was found. Results in patients with each respiratory diagnosis were compared with those in controls.
Patients with asthma, aspirin sensitivity and chronic rhinosinusitis with nasal polyps had significantly greater LTE excretion compared to the controls. There was no difference in LTE4 excretion in patients with allergic rhinitis or chronic rhinosinusitis without nasal polyps compared to controls. If history of aspirin sensitivity was adjusted for as a confounding variable, then results in patients with asthma were no longer significantly different from those without asthma. When similar adjustment was made for chronic rhinosinusitis with nasal polyps, LTE4 excretion in this condition remained significantly different. Receiver operator characteristic analysis of 24-hour urinary LTE4 measurement showed that a cutoff value of 166 pg/mg Cr suggested the presence of history of aspirin sensitivity with 89% specificity, whereas a cutoff value of 241 pg/mg Cr discriminated “challenge-confirmed” aspirin-sensitive subjects with 92% specificity. In conclusion, elevated urinary LTE4 could help alert the clinician to presence of aspirin sensitivity if the details surrounding the reaction are unclear.
The Journal of Allergy and Clinical Immunology: In Practice is an official journal of the AAAAI, focusing on practical information for the practicing clinician.