MLT GlobeQCHP exam preparation (Qatar) – page 18
749 practice MCQs for the QCHP medical laboratory exam. Level: Intermediate.
Which step belongs to a normal adaptive immune response rather than allergy?
Normal immune response begins with antigen processing and presentation. The others describe type I hypersensitivity.
Which cell is the central coordinator of adaptive immunity, directing both humoral and cellular responses?
CD4 helper T cells secrete cytokines that activate B cells, cytotoxic T cells and macrophages.
A renal biopsy from a patient with immune-complex (type III) glomerulonephritis is examined by immunofluorescence. Which finding is expected?
Circulating immune complexes lodge irregularly, giving a granular 'lumpy-bumpy' pattern. Linear IgG suggests anti-GBM (type II) disease; sensitised T cells indicate type IV.
Before solid-organ transplantation, which laboratory workup best reduces the risk of rejection?
ABO incompatibility and preformed anti-HLA antibodies cause hyperacute rejection, so ABO grouping, HLA typing and crossmatching are essential. Rh is not a major barrier in solid organs.
Latex beads coated with a soluble antigen clump when mixed with patient serum containing the matching antibody. This format is called:
Coating a soluble antigen onto inert carriers (latex, red cells) turns a precipitation reaction into visible agglutination: passive agglutination. Coagglutination uses antibody bound to staphylococcal protein A.
Which IHC result directly guides the choice of targeted therapy in breast carcinoma?
ER/PR and HER2 IHC predict response to hormonal and anti-HER2 therapy; cytokeratin only confirms epithelial origin.
A slide that focuses at 10× cannot be brought into focus with the 40× objective. The most likely cause is:
With the coverslip facing down, the slide thickness exceeds the short working distance of the 40× objective. Staining or smear thickness affects image quality but not the ability to focus.
Which of the following is NOT a recognized microtome knife profile?
Traditional steel knife profiles are plano-concave, biconcave, plane wedge and tool edge. A convex wedge is not a standard profile.
Fresh tissue is quenched at about −160 °C, then its ice is removed by sublimation under vacuum at about −40 °C before embedding. This technique is called:
Freeze-drying (lyophilization) removes water as vapour by sublimation under vacuum. Freeze-substitution instead dissolves the ice in a cold solvent such as acetone.
During microtomy, many blocks contain hard, brittle, shrunken tissue. The most likely processing fault is:
Paraffin kept well above its melting point overhardens and shrinks tissue. Water in the clearant causes soft, poorly infiltrated tissue instead.
Fine microscopic chatter in sections is commonly caused by tissue that is:
Excess time in absolute alcohol makes tissue hard and brittle, producing chatter. Under-processed tissue is soft and mushy.
Teardrop cells, nucleated RBCs with immature granulocytes (a leukoerythroblastic picture) and a 'dry tap' on marrow aspiration suggest:
In primary myelofibrosis, marrow fibrosis blocks aspiration (dry tap) and forces haematopoiesis to the spleen and liver, releasing teardrop cells and immature cells into the blood.
A narrow, sharp band in the gamma region of serum protein electrophoresis should next be confirmed by:
A narrow band suggests a monoclonal protein. Immunofixation identifies the heavy chain and light chain type and confirms monoclonality, as in myeloma or MGUS.
Which urine findings fit complete obstruction of the common bile duct?
Conjugated bilirubin backs up into blood and is water soluble, so it appears in urine. Little bilirubin reaches the gut, so urobilinogen falls and stools become pale.
A prolonged aPTT does NOT correct when the patient's plasma is mixed 1:1 with normal plasma. This suggests:
Normal plasma supplies at least 50% of every factor, enough to correct a deficiency. If the time stays prolonged, something in the patient's plasma is blocking clotting: an inhibitor.
Target cells (codocytes) are typical of all of the following EXCEPT:
Target cells have extra membrane relative to their volume: seen in liver disease, HbC and thalassemia. Spherocytes have the opposite problem, too little membrane.
Which antibody almost never causes hemolytic disease of the fetus and newborn?
Lewis antibodies are usually IgM, which cannot cross the placenta, and Lewis antigens are poorly developed on fetal red cells. Anti-D, anti-K and anti-c are IgG and can cause severe HDFN.
Which statement about ABO hemolytic disease of the newborn is correct?
Group O mothers often have IgG anti-A,B that crosses the placenta, so the first baby can be affected. Disease is usually mild because fetal A and B antigens are weak, and the DAT is often weak or negative.
Digoxin toxicity is more likely at a given serum digoxin level when the patient has:
Digoxin and potassium compete for the same site on the Na-K ATPase. Low potassium increases digoxin binding and its toxic effects, so potassium is checked with digoxin levels.
A slow-growing, rough, buff-coloured acid-fast bacillus on Lowenstein-Jensen that is niacin positive and nitrate reduction positive is most likely:
M. tuberculosis forms dry 'rough and buff' colonies after 2-6 weeks and is niacin and nitrate positive. M. kansasii is photochromogenic and M. fortuitum grows rapidly.