MLT GlobeQCHP exam preparation (Qatar) – page 33
749 practice MCQs for the QCHP medical laboratory exam. Level: Intermediate.
Lactoferrin is a component of which neutrophil granules?
Lactoferrin is a marker of the secondary (specific) granules, which appear at the myelocyte stage. Dense and alpha granules belong to platelets.
Auer rods are formed from:
Auer rods are rod-shaped fusions of primary granules and are myeloperoxidase positive. They indicate a myeloid lineage.
The large reactive lymphocytes seen in infectious mononucleosis are mainly:
EBV infects B cells, and the reactive lymphocytes on the film are mostly CD8-positive T cells attacking those infected cells.
The thrombin time mainly tests:
In the thrombin time, thrombin is added to plasma, so only the fibrinogen-to-fibrin step is tested. It is prolonged by low or abnormal fibrinogen and by thrombin inhibitors such as heparin.
Which set of results is typical of acute disseminated intravascular coagulation (DIC)?
In acute DIC, widespread clotting uses up platelets and factors (low platelets, prolonged PT/aPTT, low fibrinogen), while fibrinolysis raises D-dimer.
A woman with two previous pregnancies has a positive antibody screen at AHG and a negative autocontrol. The most likely cause is:
Reactivity with screening cells but not with her own cells points to an alloantibody, likely stimulated by pregnancy. A warm autoantibody would also make the autocontrol positive.
An antibody reacts at immediate spin but not at 37 °C or in the AHG phase. It is most likely of which class?
Large IgM antibodies agglutinate saline-suspended cells directly at room temperature. IgG antibodies usually need 37 °C incubation and AHG.
A diabetic patient's treatment was changed 3 weeks ago. Which test best shows the effect of this change on average glucose?
Fructosamine (glycated serum proteins, mainly albumin) reflects average glucose over the previous 2–3 weeks. HbA1c reflects about 2–3 months, so it responds more slowly to a recent change.
A patient with known diabetes on treatment has an HbA1c of 9.0% (75 mmol/mol). This result indicates:
HbA1c reflects average glucose over the red cell lifespan (about 2–3 months). A value of 9% is well above the usual target of below 7%, indicating poor control over that period.
A 5-year-old boy has progressive leg weakness and difficulty climbing stairs. Serum CK is 15,000 U/L. Which condition is most likely?
Duchenne muscular dystrophy causes very high serum CK (often more than 10 times normal) from early childhood because of ongoing skeletal muscle damage.
An adult has a raised alkaline phosphatase. Which additional result best supports a liver (rather than bone) source?
GGT rises in hepatobiliary disease but not in bone disease. A raised ALP with raised GGT therefore suggests a hepatobiliary source; ALP with normal GGT favours bone.
A dehydrated patient has BUN 60 mg/dL (urea 21 mmol/L) and serum creatinine 1.5 mg/dL (133 µmol/L). The BUN/creatinine ratio of 40 most suggests:
A BUN/creatinine ratio above about 20 suggests a prerenal cause such as dehydration, because urea is reabsorbed more when tubular flow is low. Liver failure and low protein intake lower urea.
A patient's serum creatinine rises from 1.0 to 2.0 mg/dL (88 to 177 µmol/L) with no change in muscle mass. The GFR has most likely:
Serum creatinine is roughly inversely proportional to GFR at steady state, so a doubling of creatinine indicates that GFR has fallen by about 50%.
Early in an acute asthma attack, a patient breathes rapidly. Which acid-base disorder is most likely at this stage?
Rapid breathing early in an asthma attack blows off CO2, lowering pCO2 and raising pH. A normal or rising pCO2 later signals tiring and impending respiratory failure.
A patient has been taking large amounts of sodium bicarbonate antacid. Which acid-base disorder is expected?
Ingesting excess bicarbonate raises plasma bicarbonate and pH, causing metabolic alkalosis.
A tall 12-year-old boy is growing very fast and has a pituitary tumor secreting excess growth hormone. This condition is called:
Excess GH before the growth plates close causes gigantism. After closure, excess GH causes acromegaly. Cretinism is congenital hypothyroidism.
A patient takes levothyroxine for primary hypothyroidism. Which test is used to check that the dose is correct?
In primary hypothyroidism the pituitary is normal, so TSH is the most sensitive guide to thyroxine replacement; the dose is adjusted to keep TSH within the reference range.
A patient has microcytic red cells with normal serum iron and normal ferritin. Which condition is more likely than iron deficiency?
Microcytosis with normal iron studies suggests a globin synthesis defect such as thalassemia trait. B12 and folate deficiency and liver disease cause macrocytosis.
Which cells are the main source of tumour necrosis factor-alpha (TNF-α) when bacterial endotoxin (LPS) enters the blood?
LPS binds TLR4 on macrophages and monocytes, which then release TNF-α, IL-1 and IL-6, driving fever and septic shock.
A patient whose spleen was removed is at particular risk of severe infection with:
The spleen is important for clearing encapsulated bacteria and making antibodies to polysaccharides. Asplenic patients can develop overwhelming pneumococcal, meningococcal and Hib sepsis.