86359

T cells; total count

Current Procedural Terminology (CPT) code 86359 represents the laboratory procedure for determining the total count of T cells in a patient's biological specimen, typically whole blood. T cells, or T lymphocytes, are a fundamental component of the adaptive immune system, playing a critical role in cell-mediated immunity. This test quantifies the total number of T cells, which are primarily identified by the presence of the CD3 surface antigen, serving as a pan-T cell marker. The total T cell count is an essential diagnostic parameter for evaluating the overall cellular immune status of a patient. It is heavily utilized in the clinical assessment of primary immunodeficiencies, such as Severe Combined Immunodeficiency (SCID) or DiGeorge syndrome, where T cell development is severely impaired or completely absent. Furthermore, this assay is integral to the management and monitoring of secondary immunodeficiencies, most notably Human Immunodeficiency Virus (HIV) infection, although specific CD4 counts (CPT 86361) are more commonly tracked for disease progression. In the realm of transplantation, monitoring total T cells helps in assessing immune reconstitution following hematopoietic stem cell transplantation (HSCT) and in managing the dosing of T cell-depleting immunosuppressive therapies, such as anti-thymocyte globulin (ATG) or alemtuzumab, to prevent or treat organ rejection. The procedure itself relies on advanced flow cytometry techniques. Following venipuncture to obtain a whole blood sample collected in an EDTA or heparinized tube, the laboratory introduces specific fluorochrome-conjugated monoclonal antibodies that bind directly to the CD3 antigens on the surface of the T cells. The red blood cells are typically lysed to isolate the leukocyte population. The prepared specimen is then processed through a flow cytometer, which uses laser light to detect the fluorescent signals emitted by the bound antibodies. By analyzing the light scattering properties and fluorescence intensity, the flow cytometer accurately enumerates the total T cells, calculating both the relative percentage of T cells among the total lymphocyte population and the absolute T cell count per microliter of blood. This highly specialized diagnostic tool provides clinicians with quantitative data necessary to formulate targeted treatment plans, predict susceptibility to opportunistic infections, and evaluate the efficacy of ongoing immunomodulatory interventions.

Clinical Indications

  • Evaluation of suspected primary immunodeficiencies such as Severe Combined Immunodeficiency (SCID), DiGeorge syndrome, or Wiskott-Aldrich syndrome.
  • Monitoring the immune status of patients with secondary immunodeficiencies, including Human Immunodeficiency Virus (HIV) infection or Acquired Immunodeficiency Syndrome (AIDS).
  • Assessment of immune reconstitution following bone marrow or hematopoietic stem cell transplantation (HSCT).
  • Monitoring the efficacy of immunosuppressive therapies, particularly T cell-depleting agents like anti-thymocyte globulin or alemtuzumab in solid organ transplant recipients.
  • Investigation of severe, recurrent, or opportunistic infections suggestive of a cellular immune defect.
  • Diagnostic evaluation and tracking of certain hematologic malignancies, such as T-cell leukemias or lymphomas.

Procedure Steps

  1. Collection of a whole blood specimen via venipuncture into a sterile tube containing an anticoagulant, typically EDTA or heparin.
  2. Transportation of the properly labeled specimen to the clinical laboratory at room temperature to preserve cellular viability and marker integrity.
  3. Incubation of a measured aliquot of the whole blood with specific fluorochrome-labeled monoclonal antibodies directed against the CD3 surface antigen (the pan-T cell marker).
  4. Addition of a chemical lysing reagent to eliminate erythrocytes (red blood cells) while preserving the leukocyte (white blood cell) populations.
  5. Washing the cell suspension with a buffer solution to remove unbound antibodies, free hemoglobin, and cellular debris.
  6. Aspiration of the prepared and stained cell suspension into a flow cytometer.
  7. Flow cytometric analysis of the cellular populations utilizing laser-induced forward scatter, side scatter, and fluorescence emission detection.
  8. Digital gating of the lymphocyte population to specifically isolate and quantify the CD3-positive T cells, determining both the relative percentage and the absolute count.
  9. Review of the generated cytometric data and histograms by a qualified laboratory scientist or pathologist, followed by the finalization of the diagnostic report.

Coding Guidelines

  • Report CPT 86359 to represent the laboratory quantification of the total T cell (CD3+) count from a patient specimen.
  • Do not report CPT 86359 in conjunction with CPT 86360 (T cells; absolute CD4 and CD8 count, including ratio) or CPT 86361 (T cells; absolute CD4 count) if the total T cell count is performed as an inherent or calculated part of those specific panels, unless payer policy expressly permits separate reimbursement.
  • When multiple distinct lymphocyte subsets are analyzed to form a comprehensive profile (e.g., B cells, NK cells, and T cells), CPT 86359 may be billed alongside CPT 86355 (B cells) and CPT 86357 (NK cells), as there is no single encompassing CPT code for this combined TBNK panel.
  • Ensure the reported ICD-10-CM diagnosis code appropriately supports the medical necessity of evaluating cellular immunity, such as a suspected or confirmed primary or secondary immunodeficiency.
  • Append modifier 91 for repeat clinical diagnostic laboratory tests if a subsequent total T cell count is medically necessary and performed on the same day for the same patient.

Associated ICD-10 Codes