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Test ID: PKU    
Phenylalanine and Tyrosine, Plasma

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Method Description Describes how the test is performed and provides a method-specific reference

Five mcL of plasma is combined with 195 mcL of water:methanol (50:50; v:v) containing deuterium (2H, denoted herein as 'd') labeled d5-Phe and d4-Tyr internal standards (IS). The mixture is vortexed and spun at 13,000 RPM for 2 minutes to precipitate protein. The supernatant is transferred to a glass vial and introduced into the API 3200 tandem mass spectrometer (MS/MS). The MS/MS is operated in the selected reaction monitoring (SRM) mode to follow the precursor to product ion transitions m/z 166.2 to 120.1 for Phe, m/z 171.2 to 125.1 for d5-Phe, m/z 182.2 to 136.2 for Tyr, and m/z 186.2 to 140.2 for d4-Tyr. Chromatography is performed using a C18 (150x4.6mm) column and total analysis time is 15 minutes.

 

The concentration of Phe is established by comparison of its ion intensity to that of the IS, d5-Phe, and Tyr is established by comparison of its ion intensity to that of the IS, d4-Tyr.

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; 10:00 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.

3 days (not reported on Saturday or Sunday)

Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result

5 days

Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded

2 weeks

Performing Laboratory Location The location of the laboratory that performs the test

Rochester