Mayo Test Catalog, (Sorted By Test Name) - Mayo Medical ...

first year and every 6 months in the second year following transplantation. For HIV patients on highly
active antiretroviral therapy (HAART), this assay every 3 to 4 months would be helpful. 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) or partial DGS (generally well-preserved thymic function). Thymus
transplants have been performed in patients with complete DGS but are not required in partial DGS.
Useful For: Evaluating thymic reconstitution in patients following hematopoietic stem cell
transplantation, chemotherapy, biological or immunomodulatory therapy, and immunosuppression
Evaluating thymic recovery in HIV-positive patients on highly active antiretroviral therapy (HAART)
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) The CD8 RTE test has limited
value in the clinical interpretation of recent thymic output in adults (see Cautions), and is likely to be of
more clinical relevance in pediatric individuals
Interpretation: The absence or reduction of T-cell receptor excision circle (TRECs), CD31+CD4
recent thymic emigrants (RTEs), and CD8+CD103+ RTEs correlates with loss of or reduced thymic
output and changes in the naive CD4 T-cell compartment. CD4 RTEs measured along with CD8 RTEs
and TREC provides a comprehensive assessment of thymopoiesis. Conversely, increases in CD8 RTEs
are of no clinical significance, and do not indicate a pathologic finding. Since CD8 RTEs is a rare
population, small changes in serial measurements may result in some values being above the reference
range; however, as noted, increases in CD8 RTEs do not have clinical significance. To evaluate immune
reconstitution or recovery of thymopoiesis post-T-cell depletion due to HSCT, immunotherapy, or other
clinical conditions, it is essential to serially measure CD4, CD8 RTE, and TREC levels. TRECs generally
show an inverse correlation with age, though there can be substantial variations in TREC count within a
given age group. Additionally, in most relevant clinical settings, a single measurement for thymic
function has very little value in discerning thymic reconstitution. Serial measurements are recommended
and the frequency can vary depending on the clinical context. A consultative report is provided.
Reference Values:
T-CELL RECEPTOR EXCISION CIRCLES (TREC) ANALYSIS FOR IMMUNE RECONSITUTION
T & B Absolute Counts
T Cells (CD3)
0-2 months: 2,500-5,500 cells/mcL*
3-5 months: 2,500-5,600 cells/mcL*
6-11 months: 1,900-5,900 cells/mcL*
12-23 months: 2,100-6,200 cells/mcL*
2-5 years: 1,400-3,700 cells/mcL*
6-11 years: 1,200-2,600 cells/mcL*
12-17 years: 1,000-2,200 cells/mcL*
> or =18 years: 582-1,992 cells/mcL
Helper Cells (CD4)
0-2 months: 1,600-4,000 cells/mcL*
3-5 months: 1,800-4,000 cells/mcL*
6-11 months: 1,400-4,300 cells/mcL*
12-23 months: 1,300-3,400 cells/mcL*
2-5 years: 700-2,200 cells/mcL*
6-11 years: 650-1,500 cells/mcL*
12-17 years: 530-1,300 cells/mcL*
> or =18 years: 401-1,532 cells/mcL
Suppressor Cells (CD8)
0-2 months: 560-1,700 cells/mcL*
3-5 months: 590-1,600 cells/mcL*
6-11 months: 500-1,700 cells/mcL*
12-23 months: 620-2,000 cells/mcL*
Current as of January 3, 2013 2:22 pm CST 800-533-1710 or 507-266-5700 or MayoMedicalLaboratories.com Page 1748