![]() Some healthy individuals can have values below the limit of detection.ĭetermination of ADA levels is not useful for carrier testing, as carriers may have ADA levels in the normal range. ![]() The limit of detection of the ADA assay is such that the result of this test should not be used as an independent diagnostic test for ADA deficiency without evidence of immunologic insufficiency. This can affect determination of response to protein vaccines. ![]() Maternal IgG crosses placenta into baby’s circulation, so IgG levels in the newborn and/or young infant can be almost normal. Immunoglobulin deficiency might not be recognized until several months after birth. Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications – OTC drugs or Herbals – that might affect the lab results? Less than 1% of ADA activity or ADA concentrations of 0.3 U/g of hemoglobin is diagnostic of the disease. This can be performed using red cells, blood mononuclear cells, or cultured fibroblasts. To differentiate ADA from other types of combined immunodeficiencies, it is necessary to assess the catalytic activity of the ADA enzyme. Patients with SCID essentially have no antibody formation and have very poor proliferation of lymphocytes. This is accomplished by assessment of: antibodies to standard protein vaccines (i.e., diphtheria and tetanus), isohemagglutinins (IgM against blood group antigens), and mitogen stimulation of lymphocytes. All immunoglobulin classes are usually decreased, but not always.Įvaluation of lymphocyte function is key for the diagnosis of the disease. Total serum immunoglobulin (Ig) levels of IgG, IgA, IgM, and IgE should be obtained. On average, SCID patients have less than 1500 lymphocytes/mL. Any infant with severe or opportunistic infection should have the full diagnostic assessment. ![]() Lymphopenia with an absolute lymphocyte count of less than 2500 cells/mL in an infant definitely requires further testing. In all ADA SCID patients, T cells, B cells, and NK cells are severely affected (T-B-NK- phenotype). The workup should start with a complete blood cell (CBC) count with differential to determine absolute lymphocyte count, as well to assess lymphoid subpopulations/markers (i.e., percentages and absolute counts of CD3+ T cells, CD4+ T cells, CD8+ T cells, CD19+ B cells, and natural killer (NK) cell markers (CD16 and CD56)). To confirm the clinical diagnosis of ADA deficiency, it is first necessary to assess the patient’s immune function. What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful? The least severe is the “partial ADA deficiency” in which affected children appear immunologically normal. ![]()
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