Test INMUNOLOGIA Y SEROLOGIA

• Key antigen-presenting cell to T lymphocytes is the dendritic cell
• Cytokines that mediate acute inflammation include IL-1, IL-6, and TNF-α
• CD8 is a characteristic marker of cytotoxic T lymphocytes

Autoimmune Diseases

• The most specific finding in the diagnosis of Systemic Lupus Erythematosus (SLE) is the presence of anti-dsDNA antibodies
• The most useful initial test for screening for systemic autoimmune disease is ANA by indirect immunofluorescence
• Anti-CCP antibodies have high specificity for Rheumatoid Arthritis

Allergies and Hypersensitivity

• The test of choice for evaluating type I hypersensitivity is skin prick test
• RAST is used to determine specific IgE

Immunodeficiencies

• Selective IgA deficiency is characterized by low or absent IgA levels with normal levels of other immunoglobulins
• In the diagnosis of HIV, Western Blot is the confirmatory technique following a reactive ELISA test

Interpretation of Tests

• The specificity of a test indicates the ability to correctly identify healthy individuals
• If a test is very sensitive, it is useful for ruling out diseases

Infectious Serology - Viral

• HBsAg indicates active Hepatitis B infection
• In HIV, a positive result in a 4th generation ELISA suggests suspicion of infection and need for confirmation
• Avidity test for IgG in toxoplasmosis helps differentiate between recent and past infection

Infectious Serology - Bacterial

• Rose Bengal test is useful for the diagnosis of Brucellosis
• FTA-ABS has greater specificity for syphilis

Infectious Serology - Parasitic

• Serologic diagnosis of hydatid disease is confirmed with ELISA
• Serologic tests including IFI and ELISA are used in the diagnosis of Chagas disease

Tumor Markers

• Beta-2 microglobulin is a tumor marker associated with Leukemias and lymphomas
• PSA is primarily used for screening of prostate cancer
• CA-125 is useful marker for tracking of ovarian cancer

New Technologies in Immunodiagnostics

• BioPlex (Multiplexing) technology allows to evaluate multiple antibodies simultaneously
• Flow cytometry is useful for the diagnosis of Leukemias and lymphomas

Integrative Clinical Cases

• For a patient with chronic fatigue, arthralgia, and a positive speckled pattern ANA, Anti-Sm test may be more specific
• For an HIV-positive patient with a CD4 count < 200, Western Blot is confirmatory for initial diagnosis
• A pregnant mother with positive IgG and low avidity for toxoplasma indicates recent infection

Review Questions - Block 3

• FTA-ABS is considered the gold standard for confirming the diagnosis of syphilis in its late latent stage
• Detection of NS1 by immunochromatography is the method of choice for early diagnosis of Dengue infection within the first 5 days of symptoms
• The combination of anti-CCP and rheumatoid factor improves the diagnostic sensitivity for rheumatoid arthritis
• Anti-TPO is the most sensitive serologic marker in autoimmune thyroiditis (Hashimoto's thyroiditis)
• p-ANCA (anti-MPO) is more likely to be found in a patient with small vessel vasculitis and rapidly progressive glomerulonephritis
• IgG avidity test is useful to differentiate between recent and old infection by Toxoplasma gondii
• CD13 is used in flow cytometry to identify myeloid lineage in actue leukemia, with CD 13 and CD 33 being characteristc markers of this
• Immunoglobulin type that first elevates during primary infeciton is IgM
• Western blot test is used as a confirmatory test in diagnosis of HIV
• HBsAg positive, Anti-HBc IgG positive, HBeAg positive indicates chronic active Hepatitis B infection