T-Cell Receptor Excision Circles (TREC) Analysis, Blood
Method Description Describes how the test is performed and provides a method-specific reference
This assay involves both preanalytical preparation of a pure cell population followed by analytical evaluation of the DNA. A modified peripheral blood mononuclear cells (PBMCs) isolation is used to prepare a nearly pure population of CD3+ T cells (adults) or total lymphocytes (pediatrics) from whole blood. The resulting purity and cell counts are obtained from the TCD4 flow cytometric assay. The cells are then lysed with Proteinase K to a predetermined target concentration, to release and expose the DNA for PCR. The genomic DNA and TREC in the cell lysates are quantified in the real-time PCR assay, in triplicate, by using a fluorescent probe specific for the TCR delta-deletion T-cell receptor excision circle (TREC) signal joint and a distinct fluorescent probe for the housekeeping gene, albumin. There is 1 copy of TREC per CD3+ T cell, while there are 2 copies of albumin in every cell. A standard curve is used to determine the absolute quantity of TREC and albumin from the fluorescence intensities measured. The albumin counts are used to determine the cell counts in each reaction and to normalize the number of TREC copies to a standard reporting unit of copies per million CD3+ T cells. The pediatric TREC counts, though measured from total lymphocytes, can be adjusted to the same reporting units using the %CD3 purity from the flow cytometric assay.(Douek DC, Vescio RA, Betts MR, et al: Assessment of thymic output in adults after hematopoietic stem cell transplantation and prediction of T cell reconstitution. Lancet 2000;355:1875-1881; Douek DC, Hill B: Personal Communication, 2005)
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.
Do not send specimen after Thursday. Specimen must be received by 10 a.m. on Friday.
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