SBB FINAL TEST PREPARATION EXAM QUESTIONS WITH 100% CORRECT ANSWERS

SBB FINAL TEST PREPARATION EXAM QUESTIONS WITH 100% CORRECT ANSWERS Given the following results, what is the probable cause of a positive reaction in the major crossmatch? IS = 0 37°C = 0 AHG = 2+ CC = ND Auto-control= 0 Check ok Alloantibody in patient serum reacting with antigen on donor cells Incorrect ABO grouping of patient or donor Autoantibody in patient serum reacting with antigen on donor cells Rouleaux - Answer-Correct: Alloantibody in patient serum reacting with antigen on donor cells Rouleaux would not appear at AHG since the residual protein in the test system would have been washed away. Autocontrol was negative in the screen, so the option of an autoantibody should be ruled out for this question. An incorrect ABO group on the donor unit would be detected at IS first, and not show negative reactions at IS and 37C with only the AHG phase positive. Recipient serum that reacted with one out of 5 donor units in the AHG phase and where the antibody screen was negative is probably due to: an alloantibody directed against a high-frequency antigen. an alloantibody directed against a low-frequency antigen. an alloantibody coating the recipient cells. an ABO mismatch. - Answer-Correct:an alloantibody directed against a low-frequency antigen. an alloantibody directed against a high-frequency antigen. <-- antibody screen would be positive and most xms incompatible an alloantibody directed against a low-frequency antigen. <-- correct; few donor/reagent RBCs will be positive for low freq antigens. When tested against patient plasma containing an antibody directed against a low freq antigen, typically an unexpected positive result will occur and require further investigation. an alloantibody coating the recipient cells. <-- the recipient (patient) rbcs are not tested in this scenario an ABO mismatch <-- incompatibility at all phases, most notably IS phase Given the following test results, what is the patient's most likely ABO type? Saliva Study: Saliva + Anti-A + A cell 2+ Saliva + Anti-B + B cell 2+ Saliva + Anti-H + O cell O Saline + Anti-H + O Cell 2+ Patient is Group AB Patient is Group O Results are inconclusive Results are invalid because the saline control is invalid - Answer-Correct: Patient is a group O In saliva studies, we use hemagglutination inhibition. This means that if the patient saliva contains an ABH substance then the saliva will neutralize the reagent, resulting in NO agglutination. So the absence of agglutination is a positive result for the substance, and agglutination means the substance is not present in the saliva. For the test to be valid, a saline control must be tested in which saline is used in place of saliva. There should be NO INHIBITION in the control, which means a positive reaction when the saline is mixed with reagent then tested against the appropriate cells. In this case, the reaction of saliva + anti-A + A cells is positive, meaning NO A SUBSTANCE was present since the agglutination was not inhibited The reaction of saliva + anti-B + B cells is positive, meaning NO B SUBSTANCE was present since the agglutination was not inhibited The reaction of saliva + anti-H + O cells is negative, meaning THERE IS H SUBSTANCE present that inhibited the agglutination. Therefore the patient has only H substance in his saliva, meaning that he is a group O. What is the most likely explanation for the following phenotyping results of the patient RBCs? D C E c e 4+ 4+ O 2+MF 4+ rr individual transfused with R1r cells R1R1 patient transfused with R1r cells R1r patient with fetal maternal hemorrhage R1R1 patient has a positive DAT - Answer-Correct: R1R1 patient transfused with R1r cells A mixed field phenotype of a patient RBC sample suggests a mixed cell population. In this case, only the c typing is MF, and the result is a 2+ so we then think that the patient is NOT c+, and the positive result is coming from the transfused cells. The fact that no other typing result is mixed field suggests that the transfused cells differing from the patient phenotype only because of the c antigen on the donor cells. So if the patient is D+C+e+, then he would be R1R1. we likely would have given Rh+ blood to this patient, so the donor has a c antigen, so the choice of R1r transfusion is the most viable of those answers given. The following results were obtained serologically using monoclonal MH04 clone sourced reagent: Anti-A Anti-B Anti-H a1 cells a2 cells B cells O cells A1Lectin 2+ 4+ 0 4+ 4+ 0+ O 0 DAT: negative XM: compatible with group O LRBCs patient status: healthy 4 year old select the answer below that best explains this pattern of reactivity. AsubB B(A) A(el) Aquired B - Answer-Correct: B(A) The B(A) phenotype is an autosomal dominant (inherited) phenotype characterized by weak A expression on group B red cells. Serologically, red cells from B(A) phenotype individuals are weak with monoclonal anti-A (<2+) and react strongly with anti-B. B(A) phenotype individuals possess a strong anti-A that is reactive with both A1 and A2 red cells in their sera. (differentiating them from AsubB patients) B(A) red cells can show varying reactivity with monoclonal anti-A reagents; however, most cases are detectable with monoclonal typing reagents containing the MH04 clone. note how in this question there are multiple clues, patient is younger and healthy, so the anomaly is not acquired (as in acquired B). Ael phenotype would be undetectable and the forward typing would be negative. Think of B(A) patients as group B with a fake A ->that's what its in parenthesis. This is a similar to acquired B where the patient is group A but acquires a "fake" group B phenotype. Which of the following antigens is associated with poly-agglutinability? K antigen Kx antigen T antigen V antigen - Answer-Correct: T antigen O - A2 - B - A2B - A1 - A1B - Bombay Listed above are several blood groups in a particular order. Which symbol should replace the dash? and What order do these represent? > and the expression of H antigen < and the expression of H antigen > and the frequency of blood groups < and the frequency of blood groups none of the above - Answer-> and the expression of H antigen Which of the following is a mechanism of an elution procedure? Disruption of structural complementarity of antigen and antibody Enhancement of structural complementarity of antigen and antibody Exchange of one immunoglobulin class for another Denaturation of membrane epitopes by chemical means - Answer-Correct: Disruption of structural complementarity of antigen and antibody Elution removes antibody molecules from the red cell membrane either by disrupting the antigen or changing conditions to favor dissociation of antibody from antigen. Many techniques are available, and no single method is best in all situations. If an eluate prepared by one technique is unsatisfactory, it may be helpful to prepare another eluate utilizing a different technique.The red cells used for any elution technique must be thoroughly washed to remove all antibody except that bound to the cells. Six washes with large volumes of saline is usually sufficient. Adequacy of washing is tested by examining saline from the last wash for the presence of antibody by the indirect antiglobulin(IAT) procedure. If antibody is detectable in the last wash, there could be enough unbound antibody molecules still present so that results obtained on testing the eluate are not valid. This assumes the possiblemixture of alloantibody and autoantibody.As soon as the elution is completed, remove the supernatant fluid and place it into a separate tube to avoid reattachment of antibody to cell stroma and a possible false negative test result. You arrive to work and the tech from the previous shift endorses a complex serologic case. The ABO results are discrepant and staff is inquiring about how to proceed. Anti-A Anti-B Anti-A,B Anti-D A1 cells B cells 2+ 3+ 4+ 0 4+ 0 DAT Polyspecific AHG DAT IgG DAT Complement DAT Saline Control W+ W+ 0 0 Antibody Identified: Anti-Fy(a) What would you recommend as the next best step? EDTA glycine acid (EGA) treat the patient red cells and repeat the ABO/Rh testing Test with a different clone of Anti-A Prewarm forward and reverse ABO typing Repeat the reverse typing with Fy(a) negative A1 and B cells - Answer-Correct: Test with a different clone of Anti-A Patient forwards as type AB and reverse types as group B. There are negative reactions in both the forward and reverse indicating low probability of spontaneous agglutination. The serologic investigation has been completed as demonstrated by the "antibody identified" section. Discrepancies arise from:- Improper performance of the test.- Weak antigens present on the red cells.- Unexpected atypical auto and/or alloantibodies present in the serum.- Abnormal substances or materials interfering with the test.- A state of disease. - subgroups Types of discrepancies: -Mixed Field Reactions and subgroups -Red Cells that Agglutinate Spontaneously -Acquired Phenotypes (ie acquired B and acquired A-like) -Decreased concentration of serum antibodies (post zone) -Increased concentration of serum/plasma antibodies (pro zone) -Rouleaux Phenomenon -Cold Auto Agglutinins -Alloantibodies that react at RT A) EDTA-Gycine Acid (EGA) treat the patient red cells and repeat the ABO/Rh testing <--The anti-D typing is negative indicating the antibody bound to patient red cell is not interfering with IS testing. B) Test with a different clone of Anti-A <-- best answer, serological results are limited by the source of the reagent. Selecting an alternative clone could determine whether the reagent is limiting the investigation. C) Prewarm forward and reverse ABO typing <-- prewarm technique is recommended in the presence of an interfering cold antibody. Since the anti-D is negative, performing a prewarm would not likely resolve the ABO discrepancy. D) Repeat the reverse typing with Fy(a) negative A1 and B cells <-- the probability of anti-Fya creating a discrepancy in the reverse is extremely low. Both A1 and B typing cells would be expected to be positive since commercial reagent reverse typing cell Which of the following primarily requires a thorough donor history to confirm the transmission of infectious agent to patient? babesia syphilis creutzfeldt-Jakob west nile virus - Answer-Correct: Creutzfeldt-Jakob CJD is a rare, progressive and fatal brain disorder that occurs in all parts of the world and has been known about for decades. CJD is different from variant CJD, the new disease in humans thought to be associated with Mad Cow disease in the United Kingdom and elsewhere. CJD appears to be an infectious disease. It has been transmitted from infected humans to patients through the transplantation of the covering of the brain (dura mater), use of contaminated brain electrodes, and injection of growth hormones derived from human pituitary glands. Rarely, CJD is associated with an hereditary predisposition; that is, it occurs in biologic or "blood" relatives (persons in the same genetic family). There is evidence that CJD can be transmitted from donors to patients through blood transfusions. There is no test for CJD that could be used to screen blood donors. This means that blood programs must take special precautions to keep CJD out of the blood supply by not taking blood donations from those who might have acquired this infection. You are considered to be at higher risk of carrying CJD if you received a dura mater (brain covering) graft. If you have had a dura mater transplant, you should not donate blood until more is known about CJD and the risk to the blood supply. If you have been diagnosed with vCJD, CJD or any other TSE or have a blood relative diagnosed with genetic CJD (e.g., fCJD, GSS, or FFI) you cannot donate. If you received an injection of cadaveric pituitary human growth hormone (hGH) you cannot donate. Human cadaveric pituitary-derived hGH was available in the U.S. from 1958 to 1985. Growth hormone received after 1985 is acceptable.