MLT GlobeQCHP exam preparation (Qatar) – page 26
749 practice MCQs for the QCHP medical laboratory exam. Level: Intermediate.
An antibody reacts only at AHG and is enhanced by ficin. It reacts with rr and R2R2 cells, not with R1R1 cells, and more strongly with c/c cells than with R1r cells. The specificity is:
Reaction with all c-positive cells, no reaction with c-negative R1R1 cells, and dosage point to anti-c. Anti-e and anti-f would not react with R2R2 cells.
When antibody titers are compared by testing samples in parallel, which change is usually considered significant?
Titration has a variation of about one dilution, so only a fourfold (two-tube) or greater change is considered real.
A cold panagglutinin reacts strongly and equally with adult A1, B and O cells and the autocontrol, but only weakly with group O cord cells. The specificity is:
Adult cells are rich in I and cord cells in i. Anti-H would react weakly with A1 cells.
An adult has a plasma volume of 3000 mL and fibrinogen of 80 mg/dL. The target is 180 mg/dL. If each cryoprecipitate unit contains 250 mg fibrinogen, how many units are needed?
Required fibrinogen = 100 mg/dL × 30 dL = 3000 mg. 3000 mg ÷ 250 mg per unit = 12 units. Forgetting to convert mL to dL gives a wrong answer.
During storage of Thawed Plasma at 1–6 °C for up to 5 days, which coagulation factor falls the most?
The labile factor VIII declines most during refrigerated storage of thawed plasma, with a smaller fall in factor V. Fibrinogen and vitamin K–dependent factors remain stable.
An apheresis platelet unit with 3 days of dating left is irradiated today. Its new expiration is:
Irradiation does not shorten platelet dating, because it does not damage platelets meaningfully. Only irradiated red cells get a shortened expiry, because of potassium leakage.
A patient's ABO group today is A, but a record from last year shows group O. Both samples were labeled correctly. The most likely problem is:
A clear change from group O to group A suggests a sample was drawn from the wrong patient (WBIT). Comparing results with historical records is required to detect this error; a new sample should be collected.
Under a maximum surgical blood order schedule (MSBOS), procedures that rarely need blood are usually managed by:
For procedures with low transfusion likelihood, type and screen is enough; units can be issued quickly if needed. This reduces unnecessary crossmatches and keeps inventory available.
A patient with sickle cell disease will start chronic transfusion. To reduce alloimmunization, which red cells are recommended?
Patients with sickle cell disease have high rates of alloimmunization. Guidelines recommend prophylactic matching for Rh (C, E, or C/c, E/e) and K antigens.
Under current US FDA rules, what is the minimum hemoglobin for an allogeneic whole blood donor?
FDA requires at least 12.5 g/dL (125 g/L) for female and 13.0 g/dL (130 g/L) for male donors. A single cut-off of 12.5 g/dL for all donors was the older rule.
A prospective donor got a tattoo 5 weeks ago at an unregulated parlour. Under current FDA guidance, the donor is deferred for:
FDA reduced the tattoo and piercing deferral from 12 months to 3 months, which covers the window period of transfusion-transmitted infections with current testing.
A US resident returns from a short holiday in a malaria-endemic area. She had no symptoms. Under current FDA guidance, she is deferred for:
Travelers to malaria-endemic areas who are not prior residents of such areas are deferred for 3 months after departure. Longer (3-year) deferrals apply to former residents and people who had malaria.
Before a plateletpheresis collection, the donor's platelet count should generally be at least:
A pre-donation platelet count of at least 150 × 10^9/L (150,000/µL) is required so that the donor's count stays safe after collection.
Two days after donating, a donor calls to report fever and diarrhea that started the day after donation. What should the blood centre do first?
Post-donation information may mean the donor was infected at donation. Components are quarantined or retrieved while the risk is assessed; permanent deferral is not automatic.
What is the role of the rosette test after delivery?
The rosette test screens for a fetomaternal hemorrhage of about 10 mL or more of fetal blood. If positive, the bleed is quantified by Kleihauer-Betke or flow cytometry.
A newborn with Rh HDFN has rising bilirubin despite intensive phototherapy. Intravenous immunoglobulin (IVIG) is given mainly to:
IVIG blocks Fc receptors on macrophages, reducing destruction of antibody-coated red cells, and may lower the need for exchange transfusion.
The Jk(a−b−) phenotype is most often found in people of:
The Kidd-null phenotype is rare overall but most frequent in Polynesians. These cells resist lysis in 2 M urea.
Cromer blood group antigens are carried on:
Cromer antigens are on DAF (CD55), a GPI-linked protein, so they are weak on PNH type III cells. CR1 carries Knops antigens.
Antibodies in the Knops system (carried on CR1, CD35) are generally:
Knops antibodies give weak, variable (HTLA-type) antiglobulin reactions because CR1 levels vary between people, and they do not cause hemolysis.
Which red cell protein carries the Yt (Cartwright) antigens?
Yt antigens are on acetylcholinesterase, a GPI-linked enzyme on red cells.