Allo-isoleucine, Blood Spot
Method Description Describes how the test is performed and provides a method-specific reference
This method quantifies valine (Val), allo-isoleucine (Allo-Ile), leucine (Ile), and leucine (Leu) using stable isotope-labeled internal standards (IS): d8-Val, d10-Allo-Ile, and d3-Leu. Branched-chain amino acids (BCAA) are extracted from a 3/16-inch dried blood spot (DBS) using a methanol:H2O (50:50) solution containing the IS. The filter plate containing the DBS and the IS is placed on an orbital shaker for 30 minutes at ambient temperature. The blood spot eluate is centrifuged into a 96-well round-bottom plate, dried under nitrogen, and reconstituted in aqueous mobile phase. BCAA are separated and detected by liquid chromatography-tandem mass spectrometry (LC-MS/MS) (SCIEX API 3200) in positive selected reaction monitoring mode. Chromatography is performed using an Applied Biosystems AAA C18 (4.6 x 150 mm) column, with mobile phases 0.1% formic acid:0.01% heptofluorobutyric acid (HFBA):H20 and 0.1% formic acid:0.01% HFBA:acetonitrile. Total analysis time is 15 minutes including column re-equilibration. (Oglesbee D, Kramer K, Lacey J, et al: Quantitative determination of allo-isoleucine and other branched chain amino acids in dried blood spots for newborn screening of maple-syrup urine disease [MSUD], unpublished Mayo method)
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.
Monday through Friday; afternoon
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