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What is the definition of antigen?
Any substance that can provoke an immune response, including the formation of antibodies.
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How are antibodies useful in diagnosis?
- 1. Diagnosis of infection
- 2. Blood-typing and cross-matching
- 3. To overcome ambiguities in histopathology where morpholgy alone is insufficient to make a diagnosis (eg, using the CD system)
- 4. Diagnosis of autoimmune disease
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What is the evidence that antibodies bind to antigen?
- 1. Antibodies neutralise toxins
- 2. Antibodies precipitate soluble antigens
- 3. Antibodies can agglutinate bacteria and red cells
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How can we detect and measure antibodies?
Agglutination of particulate antigens (eg, RBCs, bacteria, antigen-coated beads)
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What are the problems with Prostate-Specific Antigen (PSA)?
- 1. Poor sensitivity (eg, low PSA does not mean no cancer)
- 2. Poor specificity (eg, high PSA does not mean cancer)
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What are the danger signs associated with PSA levels?
- 1. High PSA in younger men
- 2. High "PSA velocity" (PSA levels rise by more than 2% per year)
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If high levels of PSA are present, what clinical procedures should occur next?
- 1.Ultrasound guided biopsy
- - If cancer is present...
- 2. Consider surgery or radiotherapy
- 3. Measure PSA after treatment
- - If PSA = 0, recurrence is unlikely
- - If PSA remains high/continues to rise, excision is incomplete or metastases are present
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What hormone is excreted in the urine during pregnancy?
Human Chorionic Gonadotrophin (HCG)
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How can we detect and measure antibodies?
By attaching a chemical label.
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