MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 21
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
Quality control for each unit of cryoprecipitate requires a minimum of:
AABB standards require at least 150 mg fibrinogen and at least 80 IU factor VIII per unit of cryoprecipitate.
Apheresis platelet QC requires that at least 90% of tested units contain:
An apheresis platelet unit must contain at least 3.0 × 10^11 platelets. The 5.5 × 10^10 value applies to whole-blood-derived platelets.
Why are platelets kept under continuous gentle agitation during storage?
Agitation in gas-permeable bags supports oxygen entry and CO2 loss, so lactic acid build-up and pH fall are limited. It does not prevent bacterial growth.
A patient has poor 1-hour platelet increments after several transfusions and has strong HLA class I antibodies. The best product is:
Immune refractoriness is most often due to HLA class I antibodies, so HLA-matched or crossmatch-compatible platelets are chosen. Washing or irradiation does not remove the antigens.
The standard gamma irradiation dose for blood components is:
AABB requires a minimum of 25 Gy to the central point and at least 15 Gy to any other part of the component, which inactivates lymphocytes.
A red cell unit with 30 days left is irradiated today. Its new expiration is:
Irradiated red cells expire 28 days after irradiation or at the original expiry, whichever comes first. Irradiation increases potassium leak.
The usual adult dose of plasma for correcting multiple factor deficiencies is:
A dose of 10–20 mL/kg raises most factor levels by about 20–30%. Smaller doses rarely correct coagulopathy.
Whole blood intended for platelet preparation should be kept before processing at:
Cooling activates platelets and shortens their survival, so whole blood for platelet production is held at room temperature until separation.
Whole-blood-derived platelets pooled in an open system expire after:
Pooling in an open system raises contamination risk, so the pool expires 4 hours after pooling. Prestorage closed-system pools keep the original expiry.
Which condition must be met before a laboratory may use an electronic (computer) crossmatch?
The computer crossmatch requires a validated system, no clinically significant antibodies, and at least two ABO determinations with one on the current sample. A negative DAT is not a requirement.
All AHG crossmatches are incompatible, all screening cells react at AHG, and the autocontrol and DAT are positive with IgG. The most likely explanation is:
Panreactivity together with a positive autocontrol and IgG DAT points to a warm autoantibody. An alloantibody to a high-frequency antigen gives a negative autocontrol in a non-transfused patient.
Modern massive transfusion protocols for trauma aim to give red cells, plasma and platelets in which approximate ratio?
Balanced resuscitation with near 1:1:1 ratios of red cells, plasma and platelets reduces dilutional coagulopathy compared with red cells plus crystalloid.
A surgical service crossmatched 300 units in one month and transfused 90. What does this indicate?
C:T ratio = 300 ÷ 90 ≈ 3.3. A ratio above about 2.0 suggests too many crossmatches; a maximum surgical blood order schedule or type-and-screen helps.
A donor reports receiving human pituitary-derived growth hormone as a child. What is the correct decision?
Pituitary-derived growth hormone has transmitted Creutzfeldt-Jakob disease, so recipients are deferred indefinitely. Recombinant growth hormone does not carry this risk.
A nurse received hepatitis B immune globulin (HBIG) after a needlestick injury. How long is she deferred from donation?
HBIG is given after possible HBV exposure, and it may also mask early infection. The donor is deferred for 12 months from the exposure.
Why is the first 30–40 mL of blood diverted into a separate pouch during collection?
The first blood may carry a core of skin with bacteria. Diverting it into a pouch, which is then used for test samples, reduces platelet contamination.
Pathogen reduction of platelets with amotosalen and UVA light works by:
Amotosalen enters cells and binds DNA and RNA; UVA light forms cross-links that block replication. This also inactivates donor T cells, so it can replace irradiation for TA-GVHD prevention.
In the older Liley method, spectrophotometric analysis of amniotic fluid at 450 nm (ΔOD450) estimates:
Bilirubin absorbs at 450 nm, so the deviation at this wavelength reflects the degree of fetal hemolysis. Results are plotted by gestational age in zones.
A D-negative woman has anti-D. Which test on maternal plasma can determine whether the fetus is D-positive without invasive sampling?
Fetal DNA circulates in maternal plasma and can be tested for the RHD gene. If the fetus is D-negative, the pregnancy is not at risk from anti-D.
Cord red cells show agglutination in all tubes, including the control. The sample was taken by squeezing the cord. What is the likely cause and remedy?
Wharton's jelly from the cord can make cells stick together and give false agglutination. Washing the cells several times with saline removes it.