Page 2627 - Hematology_ Basic Principles and Practice ( PDFDrive )

e8 Part XIII Consultative Hematology

Leukocyte Counts (Absolute and Percentage)
Summary points • Also called WBC count and differential
• Part of complete blood count
Methodology Automated hematology analyzer—flow cytometric or impedance methods, may use myeloperoxidase staining for
granulocytes, differential may be performed by automated or manual methods
Specimen requirements Whole blood: EDTA
Indications Suspected infection, hematologic disorder, or immune deficiency
Reference range Table 162.19
Interpretation • Results can vary with time of day, hormonal status, ethnicity (e.g., lower neutrophil counts in persons of African
descent)
• With infection, total white blood cell (leukocyte) count often elevated, but may be normal or low
• Predominance of neutrophils with left shift (immature myeloid precursors) suggests bacterial infection or sepsis but
nonspecific; also seen with physical or emotional stress, growth factor treatment
• Predominance of lymphocytes and/or monocytes suggests viral or atypical bacterial infection
• Eosinophilia suggests allergy, drug effect, or invasive parasitic infection
• Abnormal cells suggest leukemia, lymphoma, or myelodysplastic syndrome but can also be seen after growth factor
treatment
• Low counts suggest marrow suppression due to infection, medication, autoimmunity, toxic exposure, metabolic disorder,
bone marrow failure, myelodysplastic syndrome, leukemia, or immune deficiency
• Generally, automated differentials are more accurate, but a manual differential may be indicated if abnormal or
immature cells are present
Related tests Manual differential, peripheral smear, lymphocyte subsets
Interfering substances Clotted or hemolyzed sample
EDTA, Ethylenediaminetetraacetic acid; WBC, white blood cell.

Lymphocyte Subsets
Summary points • B-, T-, and NK-cell subsets used to diagnose and characterize immunodeficiency along with other lymphocyte function
testing
Methodology Flow cytometry
Specimen requirements Whole blood: EDTA or heparin
Indications Suspected or known immune deficiency; monitor status of HIV disease or immunomodulatory/immunosuppressive therapy
Reference range Table 162.20
Interpretation • Absolute declines in lymphocyte subsets can aid diagnosis and characterization of immune deficiencies: primarily B
cell, T cell, or combined
• T- and B-cell subsets may decline with immunomodulatory or immunosuppressive therapy
• Absolute CD4 counts—monitored in patients with HIV; may define therapy thresholds or risks for specific pathogens
• Results may vary with diurnal rhythm
Related tests Complete blood count, lymphocyte mitogen testing, lymphocyte antigen response testing, antigen-specific IgG/IgM titers
after vaccination, PPD testing for delayed type of hypersensitivity response
Interfering substances Hemolyzed sample, lipemia
EDTA, Ethylenediaminetetraacetic acid; HIV, human immunodeficiency virus; Ig, immunoglobulin; NK, natural killer; PPD, purified protein derivative.

Immunoglobulin A
Summary points • Important component of mucosal immunity—dimeric form in mucosal secretions, monomeric form in serum
• IgA deficiency may occur asymptomatically and may or may not confer increased infection risk
• Elevated levels may be seen in monoclonal gammopathies or in setting of chronic inflammation or infection (liver
disease, collagen vascular disease, autoimmune disease, chronic infections) leading to polyclonal gammopathy
Methodology Nephelometry
Specimen requirements Plain or serum separator tube
Indications Suspected immune deficiency (recurrent infections), monoclonal gammopathy, isolated IgA deficiency, anaphylactic
transfusion reaction to plasma
Reference range Table 162.21
Interpretation • Decreased with immune deficiency, celiac disease, some autoimmune diseases, medications, protein loss (nephrotic
syndrome, protein-losing enteropathy), non-IgA monoclonal gammopathy
• Increased in polyclonal hypergammaglobulinemia, monoclonal gammopathies, infections (tuberculosis, sepsis), chronic
liver disease, collagen vascular disease, autoimmune disease, IgA nephropathy
• Reference intervals may vary with methodology and patient ethnicity
Related tests IgG, IgM, serum protein electrophoresis with immunofixation
Interfering substances Lipemia, other causes of severe specimen turbidity, microbial contamination
Reference Woof JM, Kerr MA: The function of immunoglobulin A in immunity. J Pathol 208:270, 2006.

Ig, Immunoglobulin.