MLT GlobeDOH exam preparation (Abu Dhabi) – page 4
700 practice MCQs for the DOH medical laboratory exam. Level: Basic to intermediate.
A teenager with fever, sore throat and many reactive lymphocytes has a positive rapid heterophile (Monospot) test. What is the diagnosis?
Monospot detects heterophile antibodies made in Epstein–Barr virus infectious mononucleosis. Leukemias show blasts, not reactive lymphocytes with a positive heterophile test.
Rouleaux formation in a blood sample mainly affects which test result?
Stacked red cells sediment faster because of their greater mass-to-surface ratio, raising the ESR. Raised fibrinogen and globulins promote rouleaux.
Which anticoagulant prevents clotting mainly by enhancing antithrombin, thereby inactivating thrombin?
Heparin binds antithrombin and speeds its inhibition of thrombin and factor Xa. EDTA and citrate work by removing calcium; fluoride is a glycolysis inhibitor.
To obtain serum rather than plasma, blood must be collected into which tube?
Serum is the fluid left after clotting consumes fibrinogen. Anticoagulated tubes yield plasma, which still contains fibrinogen.
A patient with a poor diet and high alcohol intake develops macrocytic anemia with megaloblasts in the marrow. Which deficiency is most likely?
Folate is needed for thymidine synthesis; its lack causes megaloblastic anemia. Poor diet and alcohol commonly cause folate deficiency. Iron deficiency causes microcytosis.
Kupffer cells in the liver are tissue macrophages derived from which blood leukocyte?
Monocytes leave the blood and become resident macrophages, such as Kupffer cells in the liver and alveolar macrophages in the lung.
An 18-year-old woman has Hb 9.8 g/dL, RBC 3.6 × 10^12/L, MCV 70 fL and MCH 21.8 pg. What is expected on her blood film?
Low MCV and MCH indicate small, pale red cells, as in iron deficiency or thalassemia. Macrocytes suggest B12 or folate deficiency.
After using an oil immersion objective, how should the lens be cleaned?
Lens paper with a recommended cleaner or a small amount of alcohol removes oil safely. Xylene can dissolve lens cement and is toxic; paper and gauze can scratch.
Which cell is normally found only in bone marrow, not in circulating blood?
Megakaryocytes live in the marrow and release platelets into sinusoids; only occasional fragments reach the blood.
A CBC reports a total leukocyte count of 18 × 10^9/L in an adult. What term describes this?
Leukocytosis is a WBC count above the reference interval (about 11 × 10^9/L in adults). Leukopenia is a low count; erythrocytosis concerns red cells.
Marked rouleaux on a film and a very high ESR in an elderly patient suggest which condition?
Monoclonal immunoglobulin neutralizes red cell surface charge, causing stacking. Spherocytes, sickle cells and high hematocrit reduce rouleaux and lower the ESR.
A raised reticulocyte count is expected in which condition?
Healthy marrow responds to hemolysis by releasing more reticulocytes. Marrow failure, megaloblastic anemia and low erythropoietin all blunt this response.
A lavender-top (EDTA) tube arrives with several requests. Which test must be rejected and recollected?
Coagulation tests need citrated plasma; EDTA irreversibly binds calcium and affects factor V and VIII. EDTA samples are acceptable, even preferred, for grouping and antiglobulin testing.
Why is K2EDTA the anticoagulant of choice for a routine CBC?
EDTA chelates calcium and keeps cells well preserved for counting and smears. It does not bind iron as its anticoagulant action, and it is unsuitable for coagulation factor assays.
A CBC shows Hb 7.8 g/dL, WBC 2.1 × 10^9/L and platelets 40 × 10^9/L. This combination is termed:
Reduction of all three cell lines (red cells, leukocytes and platelets) is pancytopenia. A leukoerythroblastic picture means immature myeloid and nucleated red cells in blood.
When transferring blood from a syringe into an EDTA tube, which practice best prevents a spurious result?
Correct fill ratio and gentle inversion ensure mixing without hemolysis. Forcing blood through a needle or shaking causes hemolysis; underfilling gives excess EDTA and cell shrinkage.
Which single measure is most effective in preventing spread of infection in healthcare and laboratory settings?
Hand hygiene breaks the commonest transmission route. Under standard precautions every specimen is treated as infectious, so labelling only known positives gives false security.
An elevated ESR is most consistent with:
Acute-phase proteins such as fibrinogen and immunoglobulins promote rouleaux, raising the ESR. High red cell counts, low globulins and abnormal red cell shapes lower it.
A clinician requests a CBC with blood film. Which tube should be drawn?
EDTA preserves cell counts and morphology. Citrate is for coagulation, heparin for chemistry (it causes platelet clumping and poor staining), and fluoride-oxalate for glucose.
In a healthy adult, active hematopoiesis is found mainly in:
After childhood, red marrow retracts to the axial skeleton and proximal femur and humerus. Liver and spleen are fetal sites; the yolk sac is embryonic.