Test Catalog

Test Id : CD4RT

CD4 T-Cell Recent Thymic Emigrants, Blood

Useful For
Suggests clinical disorders or settings where the test may be helpful

Evaluating thymic reconstitution in patients following hematopoietic cell transplantation, chemotherapy, immunomodulatory therapy, and immunosuppression

 

Evaluating thymic recovery in patients who are HIV-positive and on highly active antiretroviral therapy

 

Evaluating thymic output in patients with DiGeorge syndrome or other cellular immunodeficiencies

 

Assessing the naive T-cell compartment in a variety of immunological contexts (autoimmunity, cancer, immunodeficiency, and transplantation)

 

Identification of thymic remnants post-thymectomy for malignant thymoma or as an indicator of relapse of disease (malignant thymoma) or other contexts of thymectomy

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Method Name
A short description of the method used to perform the test

Flow Cytometry

NY State Available
Indicates the status of NY State approval and if the test is orderable for NY State clients.

Yes

Reporting Name
Lists a shorter or abbreviated version of the Published Name for a test

CD4 RTE, Flow Cytometry

Aliases
Lists additional common names for a test, as an aid in searching

Acquired Immune Deficiency Syndrome (AIDS)

Immune Competence

Immune Status, Flow Cytometry

Immunodeficiency Panel, Flow Cytometry

Recent Thymic Emigrants (RTE)

RTE (Recent Thymic Emigrants)

T-Cell

CD4 T cell Count, Flow Cytometry

Quantitative CD4 T cells

Cellular Immunodeficiencies

DiGeorge syndrome

Combined immunodeficiencies

Neonatal thymic function

Severe Combined Immunodeficiency (SCID)

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Specimen Type
Describes the specimen type validated for testing

Whole Blood EDTA

Shipping Instructions

Specimens are required to be received in the laboratory weekdays and by 4 p.m. on Friday. Collect and package specimen as close to shipping time as possible. Ship specimen overnight in an Ambient Shipping Box-Critical Specimens Only (T668) following the instructions in the box.

 

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

 

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

Necessary Information

Ordering physician name and phone number are required.

Specimen Required
Defines the optimal specimen required to perform the test and the preferred volume to complete testing

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

Container/Tube: Lavender top (EDTA)

Specimen Volume 3 mL

Collection Instructions: Send whole blood specimen in original tube. Do not aliquot.

Special Instructions
Library of PDFs including pertinent information and forms related to the test

Specimen Minimum Volume
Defines the amount of sample necessary to provide a clinically relevant result as determined by the Testing Laboratory

1.5 mL

Reject Due To
Identifies specimen types and conditions that may cause the specimen to be rejected

Gross hemolysis Reject
Gross lipemia Reject

Specimen Stability Information
Provides a description of the temperatures required to transport a specimen to the performing laboratory, alternate acceptable temperatures are also included

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

Useful For
Suggests clinical disorders or settings where the test may be helpful

Evaluating thymic reconstitution in patients following hematopoietic cell transplantation, chemotherapy, immunomodulatory therapy, and immunosuppression

 

Evaluating thymic recovery in patients who are HIV-positive and on highly active antiretroviral therapy

 

Evaluating thymic output in patients with DiGeorge syndrome or other cellular immunodeficiencies

 

Assessing the naive T-cell compartment in a variety of immunological contexts (autoimmunity, cancer, immunodeficiency, and transplantation)

 

Identification of thymic remnants post-thymectomy for malignant thymoma or as an indicator of relapse of disease (malignant thymoma) or other contexts of thymectomy

Testing Algorithm
Delineates situations when tests are added to the initial order. This includes reflex and additional tests.

Clinical Information
Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Naive T cells are generated in the thymus and exported to peripheral blood to form the peripheral T-cell repertoire. There is a decrease in naive T cells derived from the thymus with age due to age-related decline in thymic output. Recent thymic emigrants (RTE) typically refers to those populations of naive T cells that have not diluted their TREC (T-cell receptor excision circles) copies by homeostatic or antigen-driven cell division. Naive T cells can be long-lived in the periphery and postpuberty, and in adults, peripheral T-cell homeostasis is maintained by a balance of thymic output and peripheral T-cell expansion and this proportion changes with age. In infants and prepubertal children, the T-cell repertoire is largely maintained by thymic-derived naive T cells. RTE express TREC indicative of naive T cells derived from the thymus.(1) In the CD4 T-cell compartment, it has been shown that naive CD45RA+ T cells coexpressing CD31 had a higher frequency of TREC compared to T cells lacking CD31.(2) The higher proportion of TREC+ naive T cells indicate a more recent thymic ontogeny since TREC can be diluted by cell division (since they are extrachromosomal).

 

It has been shown that CD31+CD4+ T cells continue to possess a relatively higher proportion of TREC despite an age-related 10-fold reduction after the neonatal period.(3) CD4 RTE (CD31+CD4+CD45RA+) have longer telomeres and higher telomerase activity, which, along with the increased frequency of TREC positivity, suggests a population of T cells with low replicative history.(3) The same study has also shown that CD31+ CD4+ T cells are an appropriate cell population to evaluate thymic reconstitution in lymphopenic children post-hematopoietic cell transplant.(3) A Mayo study (unpublished) shows that the CD31 marker correlates with TREC-enriched T cells across the spectrum of age and correlates with thymic recovery in adults after autologous hematopoietic cell transplantation.(4) CD31+ CD4 RTE have also been used to evaluate T-cell homeostatic anomalies in patients with relapsing-remitting multiple sclerosis.(5)

 

For patients with DiGeorge syndrome (DGS)-a cellular immunodeficiency associated with other congenital problems including cardiac defects, facial dysmorphism, hypoparathyroidism, and secondary hypocalcemia, and chromosome 22q11.2 deletion (in a significant proportion of patients)-measurement of thymic function provides valuable information on the functional phenotype, ie, complete DGS (associated with thymic aplasia in a minority of patients) or partial DGS (generally well-preserved thymic function seen the in the majority of patients). Thymus transplants have been performed in patients with complete DGS but are typically not required in partial DGS. There can be change in peripheral T-cell counts in DGS patients with age.(6)

Reference Values
Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

CD4 ABSOLUTE

Males

1 month-17 years: 153-1745 cells/mcL

18-70 years: 290-1,175 cells/mcL

Reference values have not been established for patients that are younger than 30 days of age.

Reference values have not been established for patients that are older than 70 years of age.

 

Females

1 month-17 years: 582-1630 cells/mcL

18-70 years: 457-1,766 cells/mcL

Reference values have not been established for patients that are younger than 30 days of age.

Reference values have not been established for patients that are older than 70 years of age.

 

CD4 RTE %

Males

1 month-17 years: 19.4-60.9%

18-25 years: 6.4-51.0%

26-55 years: 6.4-41.7%

> or =56 years: 6.4-27.7%

Reference values have not been established for patients that are younger than 30 days of age.

Reference values have not been established for patients that are older than 70 years of age.

 

Females

1 month-17 years: 25.8-68.0%

18-25 years: 6.4-51.0%

26-55 years: 6.4-41.7%

> or =56 years: 6.4-27.7%

Reference values have not been established for patients that are younger than 30 days of age.

Reference values have not been established for patients that are older than 70 years of age.

 

CD4 RTE ABSOLUTE

Males

1 month-17 years: 50.0-926.0 cells/mcL

18-70 years: 42.0-399.0 cells/mcL

Reference values have not been established for patients that are younger than 30 days of age.

Reference values have not been established for patients that are older than 70 years of age.

 

Females

1 month-17 years: 170.0-1007.0 cells/mcL

18-70 years: 42.0-832.0 cells/mcL

Reference values have not been established for patients that are younger than 30 days of age.

Reference values have not been established for patients that are older than 70 years of age.

Interpretation
Provides information to assist in interpretation of the test results

The absence or reduction of CD31+CD4 recent thymic emigrants (RTE) generally correlates with loss or reduced thymic output and changes in the naive CD4 T-cell compartment, especially in infancy and prepubertal children. The CD4RTE result must be interpreted more cautiously in adults due to age-related decline in thymic function and correlated with total CD4 T cell count and other relevant immunological data. CD4 RTE measured along with TREC (TREC / T-Cell Receptor Excision Circles (TREC) Analysis, Blood) provides a comprehensive assessment of thymopoiesis but should not be used in adults over the sixth decade of life as clinically meaningful information on thymic function is limited in the older population due to a physiological decline in thymic activity.

 

To evaluate immune reconstitution or recovery of thymopoiesis post-T-cell depletion due to post-hematopoietic cell transplant, immunotherapy, or other clinical conditions, it is helpful to systematically (serially) measure CD4RTE and TREC copies in the appropriate age groups.

Cautions
Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

The CD4 recent thymic emigrants (RTE) assay is likely to be most helpful when used along with measurement of T-cell receptor excision circles (TREC / T-Cell Receptor Excision Circles [TREC] Analysis, Blood) for appropriate correlation of thymic output, especially in context of T cell lymphopenia, post-hematopoietic cell transplant and other cellular or combined immunodeficiencies.

Supportive Data

CD4 recent thymic emigrant (RTE) pediatric reference values (95% confidence intervals) were obtained by evaluating 90 healthy individuals, ages 1 month to 17 years. There was no significant age relationship for CD4 RTE. Gender relationships for CD4 RTE were significant at the 50th percentile (p< or =0.0001). Adult reference values (95% confidence intervals) were obtained by evaluating 168 healthy adults, ages 18 to 70 years. There were significant age relationships for CD4 RTE as % CD4 T-cells.

Clinical Reference
Recommendations for in-depth reading of a clinical nature

1. Hassan J, Reen DJ: Human recent thymic emigrants-identification, expansion, and survival characteristics. J Immunol. 2001 Aug 15;167(4):1970-1976

2. Kimmig S, Przybylski GK, Schmidt CA, et al: Two subsets of naive T-helper cells with distinct T-cell receptor excision circle content in human adult peripheral blood. J Exp Med. 2002 Mar 18;195(6):789-794

3. Junge S, Kloeckener-Gruissem B, Zufferey R, et al: Correlation between recent thymic emigrants and CD31+ (PECAM-1) CD4 T-cells in normal individuals during aging and in lymphopenic children. Eur J Immunol. 2007 Nov;37(11):3270-3280

4. Dong X, Hoeltzle MV, Abraham RS: Evaluation of CD4 and CD8 recent thymic emigrants in healthy adults and children. Unpublished data 2008

5. Duszczyszyn DA, Beck JD, Antel J, et al: Altered naiveCD4 and CD8 T-cell homeostasis in patients with relapsing-remitting multiple sclerosis: thymic versus peripheral (non-thymic) mechanisms. Clin Exp Immunol. 2006 Feb;143(2):305-313

6. Nain E, Kiykim A, Ogulur I, et al. Immune system defects in DiGeorge syndrome and association with clinical course. Scand J Immunol. 2019 Nov;90(5):e12809. doi:10.1111/sji.12809

Special Instructions
Library of PDFs including pertinent information and forms related to the test

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

CD4 recent thymic emigrants are assessed in peripheral blood drawn in EDTA tubes and the test is performed as a single-tube assay. A panel of antibodies is used for the assay: CD3, CD4, CD31, CD45RA, and CD45RO, conjugated to various fluorochromes. The blood is incubated with the antibodies in the dark, followed by red blood cell lysis. Absolute counts are obtained using BD TruCount tubes. The sample is then centrifuged and resuspended in a paraformaldehyde solution for analysis on a BD FACS Canto A or Canto II flow cytometer. The data analysis is performed using BD FACS Diva software.(Unpublished Mayo method)

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

No

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.

3 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

4 days

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

Rochester

Fees
Several factors determine the fee charged to perform a test. Contact your U.S. or International Regional Manager for information about establishing a fee schedule or to learn more about resources to optimize test selection.

  • Authorized users can sign in to Test Prices for detailed fee information.
  • Clients without access to Test Prices can contact Customer Service 24 hours a day, seven days a week.
  • Prospective clients should contact their Regional Manager. For assistance, contact Customer Service.

Test Classification
Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR) product.

This test was developed using an analyte specific reagent. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information
Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Clinic Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.

CPT codes are provided by the performing laboratory.

86356

LOINC® Information
Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the order and results codes of this test. LOINC values are provided by the performing laboratory.

Test Id Test Order Name Order LOINC Value
CD4RT CD4 RTE, Flow Cytometry In Process
Result Id Test Result Name Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
29535 CD4 RTE Absolute 24467-3
89504 CD4 Absolute (cells/uL) 24467-3
29536 CD4 RTE % 8123-2
29178 Interpretation 69052-9

Test Setup Resources

Setup Files
Test setup information contains test file definition details to support order and result interfacing between Mayo Clinic Laboratories and your Laboratory Information System.

Excel | Pdf

Sample Reports
Normal and Abnormal sample reports are provided as references for report appearance.

Normal Reports | Abnormal Reports

SI Sample Reports
International System (SI) of Unit reports are provided for a limited number of tests. These reports are intended for international account use and are only available through MayoLINK accounts that have been defined to receive them.

SI Normal Reports | SI Abnormal Reports