Chapter 1: Immunohematology

Question: Four units of O neg RBCs are issued an emergency release to the ER. Immediately after the blood is issued, a blood sample and a request for 4 more units is received. The 4 additional units of O neg RBCs are issued and the type and crossmatch is started. The patient turns out to be an A pos with a negative antibody screen. The crossmatches with the first 8 O neg units are compatible and the antibody screen is negative. The ER calls requesting 6 more units. What ABO/Rh group should these next 6 Unit be?

Answer: The patient should be switched to D positive blood now. The question is whether the A units will be compatible with the passively transfused anti-A and anti-AB after receiving 8 units of O neg RBCs. Additive units contain very little residual plasma, i.e., ABO antibodies. In transfusing a small number of units, there is little risk associated in switching the patient to A pos RBC except for a possible weak transient positive DAT. Even in transfusing 8 units, there may not be a problem unless the patient is a child or small adult. A new post transfusion sample can be requested and tested for ABO antibodies either with an immediate spin crossmatch or a crossmatch carried through to AHG to detect weak ABO antibodies. If ABO antibodies are detected, only RBCs lacking the ABO antigen corresponding to the ABO antibody should be used.

Question: A group B patient needs FFP. Which blood group(s) would be acceptable?

Answer: A group B patient has B antigens on his red cells. NO FFP with anti-B will be acceptable (therefore no A or O). Group B (has anti-A) or group AB (no ABO antibodies) will be fine.

Question: A group AB patient needs blood, but ABO identical is unavailable. Which alternative goup(s) may be used?

Answer: Any blood group red cells since AB individuals have no ABO antibodies.

Question: A group B neg needs 3 units of red cells and I unit of FFP. No B neg RBCs or FFP are available. What would be the choice for both components

Answer: O neg red cells is the appropriate ABO group to select. If this is an emergency and no B neg or O neg is available, B pos or O pos would be used. The FFP should be AB since group O and A contain anti-B.

Question: A group B patient needs blood, but ABO identical blood is unavailable. Which alternative group(s) may be used?

Answer: Only group O since B individuals have anti-A and O units have no A antigens (or B antigens!)

Question: A group O patient was crossmatched with group B red cells. Will this incompatibility be detected?

Answer: Yes, the patient serum contains anti-A, -B and -A,B will show agglutination when added to the group B cells (probably a strong reaction at immediate spin)

Question: The transfusion component of choice for a bleeding patient with a prolonged bleeding time, increased APTT, decreased levels of Factor VIII antigen and impaired aggregation of platelets in response to ristocetin would be: a. Cryoprecipitate b. Factor VIII c. Fresh frozen plasma d. Platelets

Answer: a. Cryoprecipitate These laboratory data suggest a patient with Von Willebrand Syndrome. Cryoprecipitate is the only component containing Voon Willebrand factor (vWF) as well as factor VIII. Both of these are deficient in these patients. It is the vWF that is responsible for the platelet aggregating effect of ristocetin. Since the patient is bleeding, it is more likely a severe case which would warrant cryo. If the case were mild, DDAVP could be used instead. Option B is incorrect because plain Factor VIII does not contain wWF; you would need to use Factor VIII concentrates known to have vWF. Option C lists FFP as a choice. FFP has cryo in it but has too much volume; you need to give the patient concentrated factors, not volume. Option D is incorrect because you don't need platelets, you need vWF.

Question: Four units pf platelets were pooled and issued at 2:00 pm. At 7:00 pm, the ward called, said they had never transfused the platelets, and wanted to know if the platelet pool could still be used? a. No, they outdated at 6:00 pm b. No, the platelets weren't refrigerated on the ward c. Yes, they won't outdate until 8:00 pm d. Yes, they are good for 24 hours after pooling

Answer: a. No, they outdated at 6:00 pm Option B, C, and D are incorrect because none reflect the correct time or storage temperature for pooled platelets. Pooled platelets are good for 4 hours after pooling.

Question: For which of the following blood groups is it NOT necessary to run on Rh control if you are using a monoclonal/polyclonal blend anti-D. a. A neg b. A pos c. AB neg d. AB pos

Answer: b. A pos Option A and C are incorrect because an Rh control is needed for any D negative donor in order to perform the weak D test. Answer D is incorrect because a negative reaction with either the anti-A and/or anti-B reagent (as needed) shows that the patient cells are not spontaneously agglutinating and acts as the negative control. The AB positive has positive reaction with reagent anti-A and anti-B.

Question: An antibody screen gave no reactions at immediate spin or 37C, but showed a 2+ reaction when antiglobulin reagent was added. The most likely antibody causing these results would be anti- a. I b. Jka c. Leb d. P1

Answer: b. Jka Most examples of anti-Jka react only at the antiglobulin phase of testing. Options A, C, and, D are antibodies that generally react at the immediate spin/room temperature phase of testing.

Question: Cord bloods are washed prior to ABO and Rh grouping to a. expose A and B antigens b. remove Wharton's jelly c. eliminate infant's anti-i d. prevent reagent neutralization

Answer: b. Remove Wharton's jelly If cord blood is not collected appropriately, it may be contaminated with Wharton's jelly. This substance, if not removed through saline washes will cause red cells to mechanically "stick" together possibly causing false positive interpretations. Option A is incorrect because the A and B receptors on cord cells are exposed sufficiently for ABO and Rh grouping. Option C is incorrect because infants do not have anti-i. (Cord cells have i antigen). Option D is incorrect because Wharton's jelly will not neutralize anti-A, anti-B, or anti-D.

Question: The following reactions were obtained on testing maternal serum and infant cord cells. (Image) The most likely explanation for these results is a/an: a. ABO grouping error on infant b. Detection of antenatal Rh immune globulin c. Fetal-maternal hemorrhage d. False negative DAT

Answer: c. Fetal-maternal hemorrhage A positive weak D test in a postpartum patient is usually due to a fetal-maternal hemorrhage in which the fetal D positive cells have entered the maternal circulation most often at delivery. Option A is incorrect as it is plausible for an O negative mother to have an A positive infant. Option B is incorrect since the maternal antibody screen is negative (RhIG = anti-D). Option D is incorrect since hemolytic disease of the newborn is not indicated.

Question: A group A patient needs blood and FFP. The small rural hospital is out of both A blood and A FFP. Which of the following would be your first choice to transfuse to this patient? a. RBC - AB; plasma - AB b. RBC - AB; plasma - O c. RBC - O; plasma - AB d. RBC - O plasma - O

Answer: c. RBC - O; plasma - AB You must transfuse RBCs that lack the antigens corresponding to patient antibodies and transfuse plasma that lacks antibodies corresponding to the patient antigens. The patient is a group A with anti-B. Therefore, of the answer choices, you could give group O RBCs (won't react with patient's ant-B) and AB plasma (doesn't have anti-A to react with patient RBCs) Option A, B, and D are incorrect for one or more of the following: patient's anti-B would react with the AB cells and/or the anti-A in the O plasma would react with the patient's RBCs.

Question: Red blood cells which are to be tested with antiglobulin reagent are washed to: a. Remove traces of bacterial proteins b. Wash away traces of free hemoglobin c. Remove unbound serum globulin d. Expose additional antigen sites

Answer: c. Remove unbound serum globulin Antiglobulin reagent will react with any serum globulin whether it is in serum or coating red cells. Therefore, if all unbound serum is not removed, it will bind with the antiglobulin reagent and neutralize it. Options A and B do not contain globulin. Option D describes the effect of enzymes on some red cells antigens.

Question: How many units of platelet concentrates would be needed to raise the platelet count 150,000/mm3 in an average sized adult? a. 4 b. 8 c. 12 d. 15

Answer: d. 15 One unit of platelets theoretically increases the platelet count in an average sized adult 5,000 - 10,000/mm^3. 150,000 / 5,000 - 30 units of platelets.

Question: The serum in the panel below is from a patient transfused 5 months ago. The most probable antibody is: a. Anti-c b. Anti-I c. Anti-k d. Autoantibody

Answer: d. Autoantibody When serum demonstrates the same strength of reactivity with all cells tested including the autocontrol, an autoantibody is suspected. (This occurs in patients with warm autoimmune hemolytic anemia.) Option A is incorrect because cells 2 and 3 lack the c antigen but have reactivity with the serum tested. Option B is incorrect because most examples of anti-I would demonstrate activity at immediate spin/room temperature as opposed to only strong reactions at the antiglobulin phase. Option C is incorrect because the autocontrol is positive and individuals forming anti-k would be k negative. (The previous transfusion was 5 months ago and no transfused cells would be in circulation at this time to explain the positive autocontrol.)

Question: Over a two-week period, the reaction of your QC antibody show a gradual decrease from 2+ to a very weak positive with your antibody detection cells (screening cells). These results most likely indicate. a. Acceptable performance of reagents b. Inappropriate antibody specificity c. Inconsistent grading of reactions d. Deterioration of QC antibody

Answer: d. Deterioration of QC antibody Option A is incorrect because a steady decrease in reaction strength in reagent quality control signifies a loss of antigen or antibody potency. Option B would show consistent readings but at incorrect phases or with incorrect cells (QC antibody should react with all screening cells at the antiglobulin phase of testing). Option C would show a more erratic pattern of reactions (some days stronger, some days weaker).

Question: Which of the following would cause an individual to be rejected as a blood donor? a. Donor believes he had some form of hepatitis at age 9 b. Current hemoglobin is 13g/dL c. Donor is 65 years old d. Donor had chicken pox vaccination 3 weeks ago

Answer: d. Donor had chicken pox vaccination 3 weeks ago Options A-C are all ok for donations. Defer for hepatitis after age 11; 12.5 g/dL is lowest for Hgb; there is no age cut off; Option D is incorrect since Chicken Pox vaccination has a 4 week deferral.

Question: Based on the following results, select the best conclusion: The alleged father is: a. Not excluded b. Excluded by his D antigen c. Excluded by his e antigen d. Excluded by his M antigen

Answer: d. Excluded by his M antigen In relationship (paternity) testing maternity is assumed. The child's M antigen is inherited from the mother who appears to be homozygous for M (MM). The child's N antigen must be inherited from the biological father. This alleged father does not possess the N antigen and appears to be excluded. Option B is incorrect since the father does not possess a D antigen (rr=dce/dce) Option C is incorrect since the child has e as does the father.

Question: A patient has experienced febrile reactions following 2 red cell transfusions. The best component to use if subsequent transfusions are needed would be: a. Neocytes b. Packed red cells c. Washed red cells d. Leukocyte-reduced red cells

Answer: d. Leukocyte-reduced red cells Most febrile nonhemolytic (FNH) transfusion reactions are due to cytokines released from WBCs in the stored blood or to recipient antibodies to antigens on donor lymphocytes, granulocytes and platelets. Patients experiencing a FNH reaction for the first time do not always have a similar reaction with subsequent transfusion. Leukocyte-reduced products are recommended for patients who exhibit 2 or more FNH reactions. Option A and B could both still have WBC and/or cytokines. Option C is a viable option since washing would remove WBCs and cytokines, but the question asks for the BEST answer. Washing is too expensive and rarely used for this purpose since the development of leukoreduction filters. Pre-storage leukoreduction works the best since this prevents the buildup of cytokines during storage.

Question: The following results were obtained when testing a sample from a 20-year-old first-time doner. The most likely cause of this ABO discrepancy. a. Lack of immune response b. Alloantibody reacting with B cell c. Oh (Bombay) d. Subgroup of A

Answer: d. Subgroup of A This donor is a probable A2 subgroup with anti-A1. Option A is incorrect because the donor demonstrates anti-A and anti-B in his-her serum. Option B is incorrect because the reaction in an A person. Option C is incorrect because a Bombay forwards as an O. Since the patient serum tested with "O" cells (antibody screen) is negative, the antibody has to be reacting with something on the A1 cell that is not on O cells and not reacting with patients own cells - A1 antigen. Must be an anti-A1.

Question: A 24 year old A negative female was transfused with approximately 65 cc of an A positive RBC unit. How many vials of Rh Immune globulin should this woman receive? a. 0, She is not an RhIg candidate b. 2 c. 3 d. 4 e. 5

Answer: e. 5 The female is of childbearing age and is an Rh immune globulin candidate. RhIG is expected to counteract 15 cc of RBCs. 65/15 cc = 4.3. Round down to 4 (round down if the decimal is less than .5) and add 1 (safety factor) for a total of 5. (Remember, in a fetal-maternal bleed the number of cc is divided by 30.)