Time Sensitive

Ordering Recommendation

Assess thymic function in suspected severe combined immunodeficiency (SCID), DiGeorge syndrome and other T- cell immune deficiency disorders. Evaluate immune reconstitution during highly active antiviral therapy (HAART) in HIV patients and post chemotherapy and hematopoietic cell transplant.

New York DOH Approval Status

Testing is not New York state approved. Specimens from New York clients will be sent out to a New York state-approved laboratory.

Specimen Required

Patient Preparation

Lavender (EDTA) or Green (Sodium or Lithium Heparin).
New York State Clients: Lavender (EDTA).

Specimen Preparation

Transport 4 mL whole blood. (Min: 0.5 mL)
New York State Clients: Transport 3 mL whole blood in the original collection tube. (Min: 1.5 mL) Do not send to ARUP Laboratories. Specimen must be received at performing laboratory within 48 hours of collection. For specimen requirements and direct submission instructions please contact ARUP Referral Testing at (800) 242-2787, ext. 5145.

Storage/Transport Temperature

Refrigerated. Also acceptable: Room temperature.
New York State Clients: Room temperature.

Unacceptable Conditions

Cord blood. Specimens older than 72 hours. Clotted or hemolyzed specimens.


Specimens must be analyzed within 72 hours of collection.
New York State Clients: Specimens must be analyzed within 48 hours of collection.


Ambient: 72 hours; Refrigerated: 72 hours; Frozen: Unacceptable
New York State Clients: Ambient: 48 hours; Refrigerated: Unacceptable; Frozen: Unacceptable


Quantitative Flow Cytometry




1-3 days

Reference Interval

Test Number
Reference Interval
  % CD4+CD31+CD45RA+ (RTEs)
Age Reference Interval
1 Week-2 months 50-100% of CD4+
2-5 months 64-94% of CD4+
5-9 months 65-90 % of CD4+
9-15 months 61-93% of CD4+
15-24 months 40-100% of CD4+
2-5 years 37-100% of CD4+
5-10 years 41-81% of CD4+
10-16 years 31-81% of CD4+
>16 years 6-51% of CD4+

  Abs CD4+CD31+CD45RA+ (RTEs)
Age Reference Interval
1 Week-2 months 1000-4900 cells/µL
2-5 months 1400-5200 cells/µL
5-9 months 800-6200 cells/µL
9-15 months 900-5800 cells/µL
15-24 months 170-7400 cells/µL
2-5 years 190-2600 cells/µL
5-10 years 200-1700 cells/µL
10-16 years 150-1500 cells/µL
>16 years 51-609 cells/µL

Interpretive Data

Recent thymic emigrants (RTEs) CD4+CD45RA+CD31+ represent naive T-cells recently migrated from the thymus and are measured as a percent of CD4+ T-cells. A decrease or absence of RTEs is associated with a decrease or loss of thymic output in children, as seen in severe combined immunodeficiency (SCID), DiGeorge syndrome and other cellular immune deficiency disorders. RTE results should be interpreted with caution in adults due to age-related decline in thymic function. RTE assessment may also be used to evaluate immune reconstitution after hematopoietic cell transplant, post chemotherapy and in HIV patients undergoing highly active antiviral therapy (HAART). Serial measurement is recommended.

This test was developed and its performance characteristics determined by ARUP Laboratories. It has not been cleared or approved by the US Food and Drug Administration. This test was performed in a CLIA certified laboratory and is intended for clinical purposes.

Compliance Category

Laboratory Developed Test (LDT)


Hotline History


CPT Codes

86356 x3


Component Test Code* Component Chart Name LOINC
2010180 % CD4+CD31+CD45RA+ (RTEs) 8123-2
2010181 Abs CD4+CD31+CD45RA+ (RTEs) 24467-3
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.


CD4+ T-Cell Recent Thymic Emigrants (RTEs)