MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 22
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
Blood is needed for exchange transfusion of a newborn with anti-D HDFN. Which sample is preferred for antibody screening and crossmatch?
Maternal plasma has a higher antibody concentration and a larger volume, so incompatibility is easier to detect. Cord plasma can be used if a maternal sample is unavailable.
A boy with chronic granulomatous disease has acanthocytes, weak Kell antigens and absent Kx antigen on his red cells. This is the:
The McLeod phenotype is X-linked (XK gene), lacks Kx, weakens Kell antigens and causes acanthocytosis; some cases have a deletion that also causes CGD. K0 cells lack Kell antigens but have increased Kx.
The Kell-system antigen Js(a) is found mainly in people of which ancestry?
Js(a) occurs in about 20% of people of African descent and is almost absent in Europeans. Kp(a), by contrast, is a low-prevalence antigen found mainly in Europeans.
How does ficin treatment of panel cells affect reactions of anti-Jka?
Kidd antigens are resistant to proteolytic enzymes, and removing sialic acid lowers the cell charge, so anti-Jka reacts more strongly. Duffy and M/N antigens are the ones abolished.
The S and s antigens are carried on which red cell membrane protein?
S, s and U are on glycophorin B. M and N are on glycophorin A, and Gerbich antigens are on glycophorins C and D.
A person has at least one Le (FUT3) gene but is a non-secretor (se/se). The red cell Lewis phenotype is:
Without a secretor enzyme, type 1 H is not made, so Le enzyme makes only Lea. Leb needs both Le and Se genes; Le(a−b−) results when no Le gene is present.
Anti-Lea in a patient's plasma can be neutralized in vitro by adding:
Soluble Lewis substance in saliva (or plasma) of Lewis-positive people binds anti-Lea and anti-Leb. Hydatid cyst fluid neutralizes anti-P1, not Lewis antibodies.
Which substance is used to neutralize anti-P1?
Hydatid cyst fluid and pigeon egg white contain P1-like substance that inhibits anti-P1. Human milk neutralizes anti-I, and urine neutralizes anti-Sda.
The P antigen (globoside) serves as the cell receptor for which virus?
Parvovirus B19 enters erythroid precursors through globoside, so rare p and Pk people are resistant. EBV uses CD21 on B cells.
A young adult with infectious mononucleosis develops a transient cold autoantibody. Its usual specificity is:
EBV infection is associated with a transient anti-i, which rarely causes hemolysis. Anti-I is the specificity typical of Mycoplasma pneumoniae infection.
In most D-negative people of European descent, the D-negative phenotype is caused by:
Most D-negative Europeans are homozygous for deletion of RHD. An inactive RHD pseudogene (RHDψ) is a common cause in people of African descent.
Which Rh haplotype is much more common in people of African descent than in people of European descent?
R0 (Dce) is frequent in people of African ancestry but uncommon in Europeans, in whom R1 and r predominate.
Serologic weak D phenotypes such as weak D types 1–3 are mainly caused by:
Weak D results from RHD variants that lower the number of D sites, usually from changes in transmembrane or intracellular parts of the protein. Missing epitopes define partial D.
D-negative red cell stocks are low. Which patient is the most acceptable to receive D-positive red cells?
Anti-D mainly matters for future pregnancies. Switching an older male without anti-D to D-positive red cells is acceptable when supply is short.
A D-negative 30-year-old woman receives an apheresis platelet unit from a D-positive donor. What is recommended?
Platelet units contain small amounts of red cells that can sensitize to D. RhIG is recommended, especially for females of childbearing potential.
An anti-E reacts 3+ with R2R2 cells but only 1+ with R1R2 cells. This pattern is best explained by:
R2R2 cells are homozygous for E (double dose) and carry more antigen than heterozygous R1R2 cells. Most Rh antigens except D show dosage.
In ISBT numerical terminology, the D antigen is:
ISBT numbers are RH1 = D, RH2 = C, RH3 = E, RH4 = c and RH5 = e.
Febrile non-hemolytic reactions to platelet transfusions are often caused by:
White cells in the bag release cytokines such as IL-1, IL-6 and TNF during room-temperature storage. Prestorage leukocyte reduction lowers these reactions.
A patient taking an ACE inhibitor has a sudden fall in blood pressure early in a platelet transfusion, without fever or urticaria. Which mediator is most likely involved?
ACE breaks down bradykinin. In patients on ACE inhibitors, bradykinin generated during transfusion or filtration accumulates and causes hypotension, which recovers quickly when transfusion stops.
Why is hyperkalemia a concern when older irradiated red cells are used for neonatal exchange or large-volume transfusion?
Irradiation damages the red cell membrane and speeds potassium leakage during storage. For large neonatal transfusions, fresh or washed irradiated red cells are preferred.