MLT GlobeDHA exam preparation (Dubai) – page 6
700 practice MCQs for the DHA medical laboratory exam. Level: Basic to intermediate.
At what temperature must fresh frozen plasma be stored for a 12-month shelf life?
FFP is kept at ≤ −18 °C for up to 1 year (longer at ≤ −65 °C) to preserve labile factors V and VIII. Refrigeration or room temperature would destroy them.
Red cells collected in CPDA-1 without additive solution may be stored at 1–6 °C for:
Adenine in CPDA-1 supports ATP synthesis, extending storage from 21 days (CPD) to 35 days. Additive solutions such as SAGM allow 42 days.
Why were group AB individuals classically called universal recipients for red cells?
With no ABO antibodies, AB patients can receive red cells of any ABO group. Group O cells lacking A and B antigens make O the universal red-cell donor.
A group AB person's red cells and plasma contain which ABO components?
AB cells express both antigens; according to Landsteiner's rule the plasma lacks the corresponding antibodies.
Which maternal antibodies are unable to cross the placenta and therefore do not cause haemolytic disease of the fetus?
Only IgG is transported across the placenta by the neonatal Fc receptor. Pentameric IgM, like most anti-A and anti-B, stays in the maternal circulation.
Which blood component is kept at 20–24 °C with continuous agitation, with a usual shelf life of 5 days?
Cold induces platelet activation and clearance, so platelets are stored at room temperature with agitation; the bacterial risk limits storage to 5 (up to 7) days.
Which red cell group is traditionally regarded as the universal donor type?
O negative cells lack A, B and D antigens, so they can be given in emergencies before the patient's group is known.
In ACD solution, the citrate component functions as:
Citrate chelates ionised calcium, a cofactor for several coagulation steps, so blood does not clot. Dextrose provides energy.
Lewis system antibodies are characteristically:
Anti-Lea and anti-Leb are usually naturally occurring IgM cold agglutinins and rarely cause haemolytic disease of the newborn.
In forward (cell) ABO grouping, what is tested against the known anti-A and anti-B reagents?
Forward grouping identifies antigens on the patient's red cells with known antisera; reverse grouping tests the patient's serum against known reagent cells.
In reverse grouping, a patient's serum agglutinates B reagent cells but not A1 cells. The patient's ABO group is:
Serum containing anti-B but no anti-A belongs to group A. Group O serum would agglutinate both cell types.
A patient's serum contains anti-B but no anti-A, and the cells react with anti-A only. The ABO group is:
Cells with A antigen and serum with anti-B only are group A. Anti-B alone is not diagnostic because group O plasma also contains it, hence both tests.
Before routine platelet transfusion, which pretransfusion step is normally performed?
Platelets are given ABO-compatible where possible and RhD-matched for girls and women; no crossmatch is needed because few red cells are present.
A trauma patient receives synthetic colloids and balanced salt solutions in the resuscitation room. Their purpose is:
Crystalloids and colloids restore volume and perfusion but carry no oxygen, platelets or coagulation factors.
Collecting and later reinfusing a patient's own blood is known as:
Autologous transfusion (pre-deposit, haemodilution or salvage) avoids alloimmunisation and many infectious risks.
A female donor's fingerstick haemoglobin is checked. What is the lowest value that allows her to donate under AABB criteria?
AABB sets 12.5 g/dL for women and 13.0 g/dL for men. Lower values protect the donor from post-donation anaemia.
Reverse (serum) ABO grouping uses which patient specimen?
Reverse grouping detects anti-A and anti-B in the patient's serum or plasma using A1 and B reagent cells.
Testing recipient serum against donor red cells is called the:
The major crossmatch detects recipient antibodies that would destroy transfused donor cells, the most dangerous incompatibility.
A child inherits an A allele from the mother and an O allele from the father. The child's phenotype is:
The O allele produces no functional transferase, so genotype AO expresses only A antigen.
Cryoprecipitate is a rich source of:
Cryoprecipitate is the cold-insoluble fraction of FFP, concentrated in fibrinogen, FVIII, VWF, FXIII and fibronectin. Vitamin K-dependent factors remain in the supernatant.