Leukotriene E4, Urine
Method Description Describes how the test is performed and provides a method-specific reference
Leukotriene E4 (LTE4) is quantified in urine by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Deuterium-labeled(d5)-LTE4 internal standard and acetonitrile are added to all standards, controls, and specimens which are then positive pressure filtered to remove salts, particulates, and sediment from the urine. Additional sample clean-up is achieved via a Cyclone MAX mixed mode anion exchange, while a Waters Xbridge C8 analytical column is employed to focus and elute the LTE4 analyte. This eluent is transferred to an API 5000 MS/MS for instrumental analysis.
The specific transitions monitored are 438.3/333.1 m/z and 438.3/235.05 m/z for LTE4, while 443.4/338.25 and 443.4/240.15 m/z are monitored for the d5-LTE4 internal standard. The ratios of the integrated peak areas of LTE4 and its respective deuterium- labeled internal standard are used to calculate the concentration of the analyte. All LTE4 concentrations are normalized to urine creatinine levels measured using a Roche cobas enzymatic method.(Fossati P, Prencipe L, Berti G: Enzymatic creatinine assay: a new colorimetric method based on hydrogen peroxide measurement. Clin Chem 1983;29:1494-1496)
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Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Tuesday, Friday; 9 a.m.
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test