ARUP's Laboratory Test Directory

0095899: Lymphocyte Subset Panel 7 - Congenital Immunodeficiencies

Test Mnemonic: PIP
Methodology: Flow Cytometry

Performed: Sun-Sat

Reported: 1-3 days

Specimen Required:  
Collect: One 5 mL green Hemogard (sodium or lithium heparin) or one 5 mL lavender Hemogard (EDTA), or pink Hemogard (K2EDTA), labeled with the patient's name, date and time of draw.  (Min: 3 mL)  Pour-off tubes are no longer acceptable.

Transport: 5 mL whole blood at 20-25°C. (Min: 1 mL)

Pediatric Collection/Transport: 1 mL whole blood at 20-25°C.

Remarks: CRITICAL AMBIENT. Only Hemogard tubes are acceptable. Specimens must be analyzed within 48 hours of collection. Some medications may affect immunophenotyping results and should be listed on the patient test request form.
New York State Clients:  Only EDTA specimens may be submitted and must be analyzed within 30 hours of collection.

Unacceptable Conditions: Clotted, hemolyzed, refrigerated, or frozen specimens. Specimens sent in pour-off tubes. Specimens collected in ACD (yellow) tubes.  Specimens older than 48 hours.
New York State Clients: Clotted, hemolyzed, refrigerated, or frozen specimens. Specimens sent in pour-off tubes. Specimens collected in ACD (yellow) tubes or heparin. EDTA specimens older than 30 hours.

Stability: Ambient: 48 hours; Refrigerated: Unacceptable; Frozen: Unacceptable
New York State Clients: Ambient: 30 hours, Refrigerated: Unacceptable; Frozen: Unacceptable

Reference Interval:
 
Components Age: 0-11 months Age: 12-23 months Age: 2 years and older
% CD2
Absolute CD2 		55-88
3800-5300 		55-88
3100-4200 		68-91
770-2600
% CD3 (Total T-cells)
Absolute CD3 		58-85
2170-6500 		53-81
1460-5440 		58-87
710-2300
% HLA-DR
Absolute HLA-DR 		11-45
430-3300 		11-45
430-3300 		6-23
113-640
% CD4 (Helper T-cells)
Absolute CD4 		38-62
1580-4850 		31-54
1020-3600 		32-62
370-1540
% CD45RA (Naive helper T-cells)
Absolute CD45RA 		15-70
200-3400 		15-70
200-3400 		3-38
165-1030
% CD45RO (Memory helper T-cells)
Absolute CD45RO 		5-30
50-1500 		5-30
50-1500 		16-46
230-1290
% CD8 (Suppressor T-cells)
Absolute CD8 		16-34
680-2470 		16-38
570-2230 		12-45
183-1160
CD4:CD8 ratio 1.17-6.62 1.17-6.62 0.80-5.00
% CD19 (B-cells )
Absolute CD19 		11-45
430-3300 		11-45
430-3300 		6-23
117-620
% NK-cells
Absolute NK-cells 		3-19
80-340 		3-19
80-340 		4-27
72-620

Interpretive Data:
This profile screens for inherited immunodeficiencies. T-cell subsets (include naive and memory T-cells), B-cells, and NK-cells are evaluated. Primary immune deficiencies that show phenotypic abnormalities include X-linked hypogammaglobulinemia, DiGeorge syndrome, bare lymphocyte syndrome, and severe combined immunodeficiency disease (SCID).

X-linked hypogammaglobulinemia (X-linked agammaglobulinemia, Bruton's agammaglobulinemia) is caused by defective B-cell maturation secondary to mutations in the btk (Bruton's/B-cell tyrosine kinase) gene. T-cells (CD2, CD3) are normal or increased in number, and the CD4:CD8 ratio is normal or decreased.  Most of the CD4 cells express the CD45RA antigen characteristic of naive rather than memory cells. B-cells (CD19, HLA-DR) are severely decreased or absent in the peripheral blood.

X-linked hypogammaglobulinemia can be distinguished form transient hypogammaglobulinemia of infancy by the absence of B-cells. Transient hypogammaglobulinemia of infancy results from delayed capacity for immunoglobulin synthesis and spontaneously resolves with age.

Thymic aplasia (congenital thymic aplasia, DiGeorge syndrome) results in impaired T-cell maturation and function. B-cells (CD19, HLA-DR) and NK-cells (CD16/CD56) are normal but T-cells (CD2, CD3) are usually decreased with an elevated CD4:CD8 ratio. The clinical course is variable, ranging from "partial DiGeorge syndrome" to cases that resemble SCID.

SCID has multiple genetic causes, including mutations in the gamma chain of the interleukin 2 receptor and the purine degradation enzymes, adenosine deaminase, and nucleoside phosphorylase.  In adenosine deaminase deficiency, both B-cells (CD19, HLA-DR) and T-cells (CD2, CD3) are decreased in the peripheral blood.  In other forms of SCID, the lymphopenia is not as severe, but the lymphocyte count is usually less than 1,000/µL even though B-cells (CD19, HLA-DR) may be normal or increased. In contrast to thymic aplasia, any T-cells present may have an immature phenotype.

Major histocompatibility complex class II deficiency, bare lymphocyte syndrome, is caused by defective transcription of HLA class II genes; B-cells (CD19) and T-cells (CD2, CD3) are present in normal numbers, but HLA-DR is absent. The CD4+ cells are usually CD45RA+.

Common variable immunodeficiency (CVID) describes a heterogeneous group of disorders with defective antibody formation. B-cells (CD19, HLA-DR) and T-cells (CD2, CD3) are usually normal in number, although B-cells may be decreased when CVID occurs concurrently with systemic lupus erythematosus.  The CD4:CD8 ratio may be normal or decreased.

Wiskott-Aldrich syndrome includes immunodeficiency with thrombocytopenia and eczema. Lymphopenia is usually present with a progressive decline in T-cells numbers. The CD4:CD8 ratio is normal. The gene is X-linked and encodes the Wiskott-Aldrich syndrome protein.

Immunophenotyping is generally not useful in characterizing selective IgA deficiency, IgG subclass deficiencies, the hyper IgG syndrome, or hyperimmunoglobulin E syndrome (Job's syndrome).

Please refer to Statement A in the Compliance Statements section in the front of the Laboratory Test Directory.



Note:
This assay is designed for enumerating the percents and absolute cell counts of lymphocyte subsets in lysed whole blood. Whole blood is added to fluorochrome-labeled antibodies that bind specifically to cell surface antigens on lymphocytes. After incubation, lysing, and fixation, percents and absolute counts are enumerated utilizing an internal quantitation standard. Additional CBC data is not required.

CPT Code(s):
88184 First marker; 88185 x9 Each additional marker