MLT GlobeMOH exam preparation (UAE) – page 26
700 practice MCQs for the MOH medical laboratory exam. Level: Basic to intermediate.
A pre-operative patient with no bleeding history has aPTT 90 s, normal PT, correction on 1:1 mixing, and very low factor XII. What does this mean for surgery?
Factor XII deficiency greatly prolongs the aPTT but does not cause bleeding in vivo. Treatment is not required for surgery.
Thrombopoietin, the main regulator of megakaryocyte production, is produced mostly by the:
TPO is produced constantly by hepatocytes; its free level falls as it is bound by platelets and megakaryocytes. The kidney is the main source of erythropoietin.
A burn patient has many red cell fragments. The impedance platelet count may be:
Small RBC fragments (schistocytes) and very microcytic cells fall into the platelet size range and are counted as platelets. A smear check or optical method is advised.
A high immature platelet fraction (IPF) in a patient with thrombocytopenia most suggests:
IPF reflects young, RNA-rich platelets; it rises when the marrow responds to destruction such as ITP. It stays low when production fails.
Schistocytes and thrombocytopenia are present. Which result favors TTP over DIC?
In TTP the coagulation cascade is not consumed, so PT, aPTT and fibrinogen are usually normal. In DIC they are prolonged or low.
A woman with heavy menstrual bleeding has platelets of 620 × 10^9/L, microcytic anemia and low ferritin. The thrombocytosis is most likely:
Iron deficiency is a common cause of reactive thrombocytosis, which resolves with iron therapy. ET should be considered only after reactive causes are excluded.
A patient has microcytic anemia with a markedly raised RDW. Compared with thalassemia trait, this finding most favours:
Iron deficiency usually produces a heterogeneous population of cells (high RDW), whereas thalassemia trait usually shows uniform microcytes with a normal or only mildly raised RDW.
A patient has MCV 63 fL and RBC count 5.8 × 10^12/L. Using the Mentzer index, what is the result and interpretation?
Mentzer index = MCV ÷ RBC count = 63 ÷ 5.8 ≈ 10.9. A value below 13 favours thalassemia trait; above 13 favours iron deficiency. It is only a screening aid and must be confirmed.
A smear from a patient with a strong cold agglutinin shows large red cell clumps. The best way to prepare a readable smear is to:
Cold agglutinins disperse at body temperature, so warming the sample and slides reduces clumping. Refrigeration increases cold agglutination.
A patient with advanced alcoholic cirrhosis has hemolytic anemia with many red cells showing irregular spiny projections. This is known as:
In severe liver disease, abnormal lipoproteins load the red cell membrane with cholesterol, forming acanthocytes (spur cells) that are removed by the spleen. Pyruvate kinase deficiency causes echinocytes, mainly after splenectomy.
A smear shows two distinct red cell populations: normocytic normochromic cells and hypochromic microcytes. Which situation best explains this dimorphic picture?
After iron therapy, new normal cells mix with the old hypochromic microcytes, giving two populations. Thalassemia trait produces a single, uniform microcytic population.
A 25-year-old has AML with maturation. Blasts contain single long, slender Auer rods and there is a salmon-pink perinuclear hof. Which genetic finding is most likely?
t(8;21) RUNX1::RUNX1T1 typically shows AML with maturation, long thin Auer rods and good prognosis. KMT2A::AFF1 is mainly seen in infant B-ALL.
What is the main practical risk of not recognizing Pelger-Huët cells in a differential count?
Bilobed or round Pelger-Huët nuclei may be counted as bands or metamyelocytes, suggesting a left shift. The cells function normally.
A patient with fever after a tick bite has leukopenia and small basophilic berry-like clusters in the cytoplasm of neutrophils. The most likely organism is:
Anaplasma forms morulae in neutrophils (Ehrlichia chaffeensis mainly in monocytes). Babesia infects red cells, not leukocytes.
Post-streptococcal glomerulonephritis with granular deposits and low C3 is an example of which hypersensitivity type?
Circulating immune complexes deposit in glomeruli and activate complement, giving a lumpy-bumpy granular pattern and low C3. This is type III (immune complex) hypersensitivity.
A patient develops fever, rash, arthralgia and proteinuria 8–10 days after receiving antivenom made in horses. The most likely mechanism is:
Serum sickness is a type III reaction: antibodies to foreign serum proteins form immune complexes about 1–2 weeks after exposure. Anaphylaxis would occur within minutes.
Papain digestion of an IgG molecule produces:
Papain cuts above the hinge disulfide bonds, giving two monovalent Fab fragments and one crystallizable Fc fragment. Pepsin cuts below the hinge, giving one divalent F(ab')2.
In Ouchterlony double diffusion, precipitin lines that cross each other completely indicate:
Crossing lines mean the two antigens share no epitopes (non-identity). Fused arcs indicate identity and a spur indicates partial identity.
Panel reactive antibody (PRA) or calculated PRA (cPRA) in a transplant candidate estimates:
cPRA expresses the percentage of the donor population with HLA antigens to which the candidate has antibodies. A high cPRA means the patient is highly sensitised and harder to match.
Most clinical osmometers measure osmolality by detecting which colligative property of the sample?
Freezing point depression osmometers measure how much solutes lower the freezing point (1 osmol/kg lowers it by 1.86 °C). Refractive index is not a colligative property.