The basic tests performed when an immunodeficiency is suspected should include a full blood count (including accurate lymphocyte and granulocyte counts) and immunoglobulin levels (the three most important types of antibodies: IgG, IgA and IgM). Other tests are performed depending on the suspected disorder: * Quantification of the different types of mononuclear cells in the blood (i.e. lymphocytes and monocytes): different groups of T lymphocytes (dependent on their cell surface markers, e.g. CD4+, CD8+, CD3+, TCRαβ and TCRγδ), groups of B lymphocytes (CD19, CD20, CD21 and immunoglobulin), natural killer cells and monocytes (CD14+), as well as activation markers: HLA-DR, CD25, CD80 (B cells). * Tests for T cell function: skin tests for delayed-type hypersensitivity, cell responses to mitogens and allogeneic cells, cytokine production by cells * Tests for B cell function: antibodies to routine immunisations and commonly acquired infections, quantification of IgG subclasses * Tests for phagocyte function: reduction of nitro blue tetrazolium chloride, assays of chemotaxis, bactericidal activity. Due to the rarity of many<unk> es, many of the above tests are highly specialised and tend to be performed in research laboratories. Criteria for diagnosis were agreed in 1999. For instance, an antibody deficiency can be diagnosed in the presence of low immunoglobulins, recurrent infections and failure of the development of antibodies on exposure to antigens. The 1999 criteria also distinguish between "definitive", "probable" and "possible" in the diagnosis of<unk> . "Definitive" diagnosis is made when it is likely that in 20 years, the patient has a >98% chance of the same diagnosis being made; this level of diagnosis is achievable with the detection of a genetic mutation or very specific circumstantial abnormalities. "Probable" diagnosis is made when no genetic diagnosis can be made, but the patient has all other characteristics of a particular disease; the chance of the same diagnosis being made 20 years later is estimated to be 85-97%. Finally, a "possible" diagnosis is made when the patient has only some of the characteristics of a disease which are present, but not all. Classifications There are many forms of<unk> . The International Union of Immunological Societies recognizes nine classes of<unk> es, totaling over 120 conditions. A 2014 update of the classification guide added a 9th category and added 30 new gene defects from the prior 2009 version. , there are approximately 430 forms of<unk>  that have been<unk> entified. Different forms of<unk>  have different mechanisms. Rough categorizations of conditions divide them into humoral immunity disorders, T-cell and B-cell disorders, phagocytic disorders, and complement disorders. Most forms of<unk>  are very rare. IgA deficiency is an exception, and is present in 1 in 500 people. Some of the more frequently seen forms of<unk>  include common variable immunodeficiency, severe combined immunodeficiency, X-linked agammaglobulinemia, Wiskott–Aldrich syndrome, DiGeorge syndrome, ataxia–telangiectasia,
Primary immunodeficiency
Combined immunodeficiencies
Severe combined immunodeficiency
Selective immunoglobulin A deficiency
Common variable immunodeficiency
IgG deficiency
X-linked agammaglobulinemia
Adult-onset immunodeficiency syndrome