PHD - Clinical Immunological Tests (Self) Flashcards
What is the difference between a direct and indirect Coomb’s test and what does it test for?
Coomb’s tests are used to determine the presence of autohemolytic anemia. Direct - detects antibodies and/or complement factors directly on RBCs Indirect - detects serum antibodies to RBCs
In protein electrophoresis, what protein is most negatively charged?
Gamma proteins (immunoglobulins)
A 60-year-old asymptomatic female has a positive ANA with a speckled pattern at a dilution of 1:40 (low titer). This test is repeated at another lab and is negative. The most likely explanation is: A. The first test is a false positive B. The patient has an autoimmune disease that is not lupus C. The patient has lupus D. The second lab is incompetent
A. The first test was a false positive As you age, the likelihood that you will have a false positive on an ANA increases. Lupus can be ruled out because the ANA would be a homogenous pattern, and you would need to follow up with anti-DNA and anti-Smith to confirm. Speckled pattern ANA indicates some form of autoimmune disease, but is not specific. However, the patient’s age and the second lab getting a negative ANA would increase the likelihood that this was a false positive.
What is the zeta potential of RBCs? What happens when this is elminated?
The zeta potential is the negative charge associated with the RBC membrane. This charge repels RBCs so that they do not clump together in solution. When eliminated (as in a sample with increased positively charged proteins) this would get rid of zeta potential and cause clumping of RBCs, leading to an increased sedimentation (SED) rate.
What two things should be tested for when screening for rheumatoid arthritis?
- Rheumatoid factor (IgM against the Fc portion of IgG) 2. Anti-citrullinated peptide (anti-CCP) antibodies
An elevated SED rate is a sign that the patient: A. Has systemic inflammation B. Is anemic C. Leads a sedentary lifestyle D. Will have a low C-reactive protein
A. Has a systemic inflammation Remember that an increased SED rate occurs with an increase in concentration of positively-charged proteins in the serum that negates the zeta potential of RBCs, causing them to clump. Positively-charged proteins (fibrinogen, C-reactive protein) are released by the liver in response to chronic inflammation.
Which complement factor is used in both alternative and classical pathways? Which ones are strictly in classical?
Used in both: C3 Classical only: C1(q,r,s), C2, and C4
In a plasma cell which produces only one type of immunoglobin, what would you expect to see in a protein electrophoresis?
Monoclonal (M) spike An M spike is an increase in the gamma peak of a protein electrophoresis, indicating increased production of immunoglobulins.
Differentiate between direct and indirect immunofluoresence in automimmunity analysis tests.
Direct - measures immunoglobulins directly in the patient’s tissues. Indirect - measures immunoglobulins indirectly in the patients serum
What is a sedimentation (SED) rate and what does it indicate?
SED rate is the time it takes for RBCs to clump and settle out of serum. Increased SED rate indicates that the zeta potential has been removed, most likely caused by fibrinogen, C-reactive proteins, and other acute phase proteins. These proteins are indicators of chronic inflammation.
A positive P-ANCA would suggest that which of the following is present: A. Antibodies to myeloperoxidase B. IgE antibodies to bee venom C. Red cell antibodies D. Rheumatoid factor
A. Antibodies to myeloperoxidase Remember that P-ANCA stands for perinuclear-anti-netrophil cytoplasmic antibody. This pattern indicates antibodies against myeloperoxidase (MPO)
What is the term used to describe an increased amount of free light chains in the blood?
Hyperglobulinemia
Differentiate between C-ANCA and P-ANCA in what is being stained.
C-ANCA stains cytoplasm P-ANCA stains nucleus
How is an anti-cyclic citrullinated peptide formed? The presence of this is indicative of what condition?
CCPs are formed by conversion of arginine to citrulline via the enzyme peptidyl arginine deiminase (PADI). PADI removes a nitrogen from arginine and replaces it with an oxygen to form citrulline.
In protein electrophoresis, what are the five categories that you should expect proteins to be categorized in? Within which category are antibodies localized?
Categories from most positively to most negatively charged on a gel: 1. Albumin 2. Alpha-1 (a1-antitrypsin, TBG, transcortin) 3. Alpha-2 (haptoglobin, ceruloplasmin, a2 macroglobulin) 4. Beta (transferrin, beta2-lipoprotein) 5. Gamma (immunoglobulins) - only negatively charged
In the immunofixation sample below, a sample was obtained from protein gel electrophoresis and smeared. In the patient serum portion below, what is the immunoglobulin of the patient? What condition may this patient have?
Immunoglobulin in the patient is IgG with only kappa light chains.
Because all immunoglobulins are the same, the patient most likely has a monoclonal B-cell expansion, such as multiple myeloma.
