Test Catalog

Test ID: PKU    
Phenylalanine and Tyrosine, Plasma

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

This method quantifies phenylalanine (Phe) and tyrosine (Tyr) using stable isotope-labeled internal standards (IS): d5-Phe and d4-Tyr. Phe and Tyr are extracted from plasma using methanol:water (50:50) solution containing the IS. The mixture is vortexed and centrifuged to precipitate protein. The supernatant is diluted and then introduced into the tandem mass spectrometer (MS/MS). The concentration of Phe and Tyr are established by comparison of the ion intensity with that of the IS (d5-Phe and d4-Tyr, respectively).(Unpublished Mayo method)

PDF Report Indicates whether the report includes an additional document with charts, images or other enriched information


Day(s) Performed Outlines the days the test is performed. This field reflects the day that the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time before the test is performed. Some tests are listed as continuously performed, which means that assays are performed multiple times during the day.

Monday through Friday

Report Available The interval of time (receipt of sample at Mayo Clinic Laboratories to results available) taking into account standard setup days and weekends. The first day is the time that it typically takes for a result to be available. The last day is the time it might take, accounting for any necessary repeated testing.

2 to 4 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 Indicates the location of the laboratory that performs the test