Sign in →

Test Code TREC T-Cell Receptor Excision Circles (TREC) Analysis, Blood

Reporting Name


Performing Laboratory

Mayo Clinic Laboratories in Rochester

Useful For

Measuring T-cell output or reconstitution (thymopoiesis) following hematopoietic cell transplantation or highly active antiretroviral therapy


Evaluating thymic function in patients with cellular or combined primary immunodeficiencies, or receiving immunotherapy or cancer vaccines


Assessing T-cell recovery following thymus transplants for DiGeorge syndrome

Method Name

Real-Time Quantitative Polymerase Chain Reaction (PCR)

Specimen Type

Whole Blood EDTA

Additional Testing Requirements

This assay is useful for longitudinal assessment of thymic function and naive T-cell production. For comprehensive thymic function analysis on pediatric patients or posthematopoietic cell transplantation, order this test and CD4RT / CD4 T-Cell Recent Thymic Emigrants (RTE).

Shipping Instructions

Specimens are required to be received in the laboratory weekdays and by 4 p.m. on Friday. Draw and package specimen as close to shipping time as possible.


It is recommended that specimens arrive within 24 hours of draw.


Samples arriving on the weekend and observed holidays may be canceled.

Necessary Information

Ordering physician's name and phone number are required.

Specimen Required

For serial monitoring, we recommend that specimen draws be performed at the same time of day.


Supplies: Ambient Shipping Box-Critical Specimens Only (T668)

Container/Tube: Lavender top (EDTA)

Specimen Volume:

Adults: 10 mL


-Preferred volume for >1 year = 5 mL

-Preferred volume for ≤1 year old = 3 mL

Collection Instructions:

1. Do not draw specimen through a butterfly needle.

2. Send specimen in original tube. Do not aliquot.

Specimen Minimum Volume

Adults: 10 mL/Pediatrics: 1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Whole Blood EDTA Ambient 48 hours PURPLE OR PINK TOP/EDTA

Reject Due To

Gross hemolysis Reject
Gross lipemia Reject

Reference Values

The appropriate age-related reference values will be provided on the report.


T-cell receptor excision circles (TRECs) generally show an inverse correlation with age, though there can be substantial variations in TREC copies relative to T-cell count within a given age group.


Following hematopoietic cell transplantation (HCT), highly active antiretroviral therapy (HAART), thymic transplants, etc, TREC typically increases from absent or very low levels (below age-matched reference range) to baseline levels or exceeds baseline levels, showing evidence of thymic rebound, which is consistent with recovery of thymic output and T-cell reconstitution.


When a patient is being monitored for thymic recovery posttransplant treatment, this assay recommends that a pretransplant (prior to myeloablative or nonmyeloablative conditioning) or a pretreatment baseline specimen be provided so that appropriate comparisons can be made between the pre- and posttransplant treatment specimens. Since there is substantial variability between individuals in TREC copies, the best comparison is made to the patient's own baseline specimen rather than the reference range (which provides a guideline for TREC copies for age-matched healthy controls).


A consultative report will be generated for each patient.

Day(s) and Time(s) Performed


Do not send specimen after Thursday. Specimen must be received by 10 a.m. on Friday.

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the U.S. Food and Drug Administration.

CPT Code Information

81479-Unlisted molecular pathology procedure

LOINC Code Information

Test ID Test Order Name Order LOINC Value
TREC TREC, B In Process


Result ID Test Result Name Result LOINC Value
28306 CD3 T Cells 8122-4
28307 CD4 T Cells 24467-3
28308 CD8 T Cells 14135-8
87959 TREC Copies 62320-7
30292 Interpretation 69048-7
35200 Reviewed by 18771-6

Special Instructions


TREC Assay Patient Information (T589) in Special Instructions