From the Guidelines
To check immune status, the most essential laboratory tests include a complete blood count (CBC) with differential, immunoglobulin levels (IgG, IgA, IgM, IgE), lymphocyte subset analysis using flow cytometry, and complement levels (C3, C4, CH50) as outlined in the practice parameter for the diagnosis and management of primary immunodeficiency 1. These tests provide a comprehensive picture of immune function by evaluating different components of the immune system, including innate and adaptive immunity. The initial laboratory examination of humoral immunity consists of measuring levels of various immunoglobulin isotypes (IgG, IgA, IgM, and possibly IgG subclasses) in serum, as well as a measure of function or specific antibody production, which should include both protein and polysaccharide antigens 1. Some key points to consider when evaluating immune status include:
- Measuring white blood cell counts, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils through a CBC with differential
- Assessing antibody production capacity through immunoglobulin levels (IgG, IgA, IgM, IgE)
- Evaluating specific immune cell populations like CD4+ T cells, CD8+ T cells, B cells, and NK cells using flow cytometry
- Assessing the complement pathway through levels of C3, C4, and CH50
- Considering functional immune tests such as vaccine response testing and delayed-type hypersensitivity skin tests to assess T cell function
- Testing for HIV when immunodeficiency is suspected, and autoantibody tests like ANA, RF, and specific autoantibodies for suspected autoimmune conditions. It is also important to report absolute lymphocyte subset values when an automated complete blood cell (CBC) count (WBC and differential) has been performed from blood drawn at the same time as that for immunophenotyping 1. Overall, these tests help clinicians identify specific deficiencies or abnormalities that may require treatment or monitoring, prioritizing morbidity, mortality, and quality of life as the outcome.
From the Research
Lab Tests to Check Immune Status
To check immune status, several lab tests can be conducted, including:
Components of Complete Blood Count
The components of a CBC include:
- Red blood cell count
- Hemoglobin
- Hematocrit
- Red blood cell indices (including the mean cell volume, mean cell hemoglobin, mean cell hemoglobin concentration, and red cell distribution width)
- Reticulocyte count
- White blood cell count and differential
- Platelet count These components can provide valuable information about the immune system and can be used to predict the risk of certain diseases, such as cardiovascular disease and metabolic syndrome 3
Markers to Predict Diseases
Several markers can be used to predict cardiovascular and metabolic diseases, including:
- White blood cell (WBC) count
- Neutrophil-to-lymphocyte ratio (NLR)
- Hemoglobin (Hb)
- Mean corpuscular volume (MCV)
- Red cell distribution width (RDW)
- Platelet count
- Mean platelet volume (MPV)
- Platelet-to-lymphocyte ratio (PLR) 3