Leukotriene E4, 24 Hour Urine (Sendout)

Useful For:

• Aiding in the evaluation of patients at-risk for mast cell activation syndrome (eg, systemic mastocytosis, IgE-mediated allergies, or aspirin-exacerbated respiratory disease)
• Increased excretion of LTE4 is nonspecific and should not be used alone to make a clinical diagnosis of a MC activation disease.

Test Highlights: Quantitation of urinary metabolites of histamine, prostaglandin D2, and leukotriene E4 may provide significant clues for the diagnosis and management of symptomatic patients with both clonal and nonclonal mast cell activation syndromes. The presence of 1 or more elevated levels of these biomarkers in urine greatly narrows diagnostic possibilities for causes of symptoms, informs the practitioner what specific metabolic pathways are involved, and targets the treatment in a specific, personalized fashion.

For an optimal evaluation, testing for urinary leukotriene E4 should be accompanied with laboratory investigations for the presence of serum Tryptase [TRYPT], 2,3 Dinor 11 Beta Prostaglandin F2 Alpha, 24h Urine (Sendout) [RU23BP], and N Methylhistamine, 24 Hour Urine (Sendout) [RUNMHT].

Systemic mastocytosis is a heterogenous disease and lack of elevated LTE4 does not exclude the diagnosis of mast cell disease.

Increased excretion of LTE4 has also been reported in the following conditions: asthma, eosinophilic pneumonia, respiratory syncytial virus infection, atopic dermatitis, Crohn disease, and rheumatoid arthritis.

Ordering Requirements: Pre-approved for UW Medicine Allergy Clinics. Orders from other locations require Laboratory Medicine Resident (LMR) approval.

Ordering Note: This test is for timed urine collections only. For random urine collections, refer to Leukotriene E4 (LTE4), Random Urine (Sendout) [OLTG #1070].

Leukotriene E4: Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

Creatinine: Enzymatic Colorimetric Assay

Reference Range:

Interpretation: Elevated urinary leukotriene E4 (LTE4) concentrations above 104 pg/mg creatinine may be suggestive of mast cell activation syndrome if compatible features of disease are present.

24 Hour Collection:

• Start collection within a few hours of symptom onset.
• Collect urine for 24 hours in a preservative-free amber polyethylene 24-hr urine collection container. Record the collection interval.
• Refrigerate urine within 4 hours of completion of collection.

Outside Laboratories:

• Mix specimen well. Measure and record total volume. Document the total volume and collection interval on the DLMP requisition.
• Aliquot 5 mL urine to a plastic screw-cap vial, leaving room for expansion. Freeze urine at -20°C while awaiting shipment. Transport samples on dry ice.

• Mix specimen well. Measure and record total volume.
• Document the collection interval and total volume on the requisition. Provide Sendouts with a copy.
• Aliquot urine into a plastic screw-top vial, leaving room at the top for expansion. Freeze specimen at -20°C.

Result-at-entry:

• RULTIN (Leukotriene E4 Collection Interval): <Enter the interval in hr>
• RULTTV (Leukotriene E4 Total Volume): <Enter the volume in mL>

Sendouts:

• Order Mayo Test: TLTE4.
• Interfaced: Yes.