MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 2
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
ABO antigens are important in solid organ transplantation mainly because they are:
ABH are histo-blood group antigens found on endothelium and many epithelial cells. ABO-incompatible grafts risk hyperacute rejection from recipient anti-A or anti-B.
Compared with adult red cells, ABO antigens on newborn red cells are:
A and B antigens are present at birth but weaker, as fewer branched chains are formed. Adult strength develops over the first few years of life.
Most routine anti-A and anti-B typing reagents used today are:
Current ABO reagents are mostly mouse monoclonal IgM antibodies, which are standardized and strong. Human polyclonal sera were used in the past; lectins serve special purposes.
In tube ABO typing, a mixed-field reaction looks like:
Mixed field shows agglutinates alongside a large population of unagglutinated cells, indicating two cell populations. Coin-like stacking is rouleaux.
In a column (gel) agglutination test, a strong positive (4+) reaction appears as:
Large agglutinates cannot enter the gel and stay at the top. Unagglutinated cells pass through and form a button at the bottom, which is a negative reaction.
The sensitization step of the indirect antiglobulin test is performed at:
IgG antibodies bind best at body temperature, so plasma and cells are incubated at 37 °C before washing and adding AHG. 56 °C is used for heat elution.
What is the function of adenine in CPDA-1?
Adenine allows red cells to resynthesize ATP, improving post-transfusion survival and extending storage. Citrate, not adenine, prevents clotting by binding calcium.
Red blood cell units must be stored at:
Red cells are stored refrigerated at 1–6 °C. The wider 1–10 °C range applies to transport, not storage.
The main purpose of washing red cells is to:
Saline washing removes about 99% of plasma proteins, useful for recurrent severe allergic reactions or IgA-deficient patients. It does not prevent GVHD.
Platelets have the highest risk of bacterial contamination among blood components mainly because they are:
Storage at 20–24 °C allows skin bacteria to multiply, unlike refrigerated red cells or frozen plasma.
In a stable adult without bleeding, one red cell unit is expected to raise the hemoglobin by about:
One unit usually raises hemoglobin by about 10 g/L (1 g/dL) and hematocrit by about 3% in an average adult.
A group B patient needs plasma. Which plasma groups are ABO-compatible?
Plasma must lack antibodies to the recipient's antigens. Group B plasma (anti-A) and AB plasma (no antibodies) are safe; group O plasma contains anti-B.
Blood is released before pretransfusion testing is complete. Which record is required?
Emergency release requires the requesting physician to document that the clinical situation justified transfusion before testing was finished. Testing is completed afterwards and abnormalities reported at once.
Which recently given vaccine does NOT require donor deferral in a donor who feels well?
Toxoids and inactivated vaccines do not cause deferral in symptom-free donors. Live attenuated vaccines such as varicella, oral typhoid and yellow fever require a temporary deferral of 2–4 weeks.
During donation, a donor becomes pale, sweaty and dizzy with a slow pulse. What is the correct first action?
These are signs of a vasovagal reaction. The needle is removed, the donor lies flat with legs raised, and cold compresses are applied; the collection is not continued.
The Kidd glycoprotein functions in the red cell membrane as a:
Kidd antigens are on the urea transporter (SLC14A1), which helps red cells keep osmotic stability in the renal medulla. The anion exchanger (band 3) carries the Diego antigens.
Lewis antigens on red cells are:
Lewis antigens are made in tissues and taken up passively onto red cells from plasma. This is why the Lewis type can change, e.g. in pregnancy. Non-secretors with a Le gene still express Lea.
A D-negative woman received antenatal RhIG at 28 weeks. She now delivers a D-positive baby. What is needed?
Antenatal RhIG does not replace the postpartum dose. After a D-positive birth she needs a fetomaternal hemorrhage screen and at least one dose.
A patient with thalassemia major receives regular red cell transfusions. Which long-term complication is monitored with serum ferritin?
Each red cell unit contains about 200–250 mg of iron, which the body cannot excrete. Ferritin is used to monitor iron load and guide chelation therapy.
A venous sample was mistakenly labelled as arterial. Which result pattern most suggests this?
Mixed venous blood normally has pO2 about 35–45 mmHg and pCO2 a few mmHg higher than arterial, with slightly lower pH. Unexpected hypoxemia in a well patient should prompt this question.