MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 19
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
A 32-year-old with acute leukemia develops prolonged PT and aPTT, low fibrinogen and raised D-dimer at diagnosis. Blasts contain many granules and bundles of Auer rods. Which genetic change is most likely?
Heavily granular promyelocytes with bundles of Auer rods ('faggot cells') plus DIC is classic acute promyelocytic leukemia, defined by t(15;17) PML::RARA. Granule procoagulants trigger DIC, which is why APL is a medical emergency.
A patient has a WBC of 60 × 10^9/L with a left shift. Which result best supports a leukemoid reaction rather than chronic myeloid leukemia?
Neutrophils in a leukemoid reaction (infection, inflammation) are activated and have a high LAP score. In CML the LAP score is characteristically low. Basophilia, splenomegaly and BCR::ABL1 all favour CML.
Mononuclear cells with fine cytoplasmic projections are found in a patient with pancytopenia and splenomegaly. Which cytochemical stain is classically positive in these cells?
The 'hairy' projections plus pancytopenia and splenomegaly point to hairy cell leukemia, whose cells are TRAP positive. Today flow cytometry (CD11c, CD25, CD103) and BRAF V600E testing are also used.
Blasts are positive for non-specific esterase (alpha-naphthyl acetate), and the staining disappears when sodium fluoride is added. The blasts are most likely:
Monocytic cells stain strongly with non-specific esterase, and this activity is inhibited by sodium fluoride. Granulocytes are positive for specific esterase (naphthol AS-D chloroacetate) instead.
Gum hypertrophy and skin infiltration at diagnosis of acute leukemia are most typical of which type?
Leukemic monocytes readily leave the blood and infiltrate tissues such as gums, skin and the CNS. Gingival hyperplasia is a classic clinical clue to acute monocytic or myelomonocytic leukemia.
According to the WHO classification, the usual minimum blast percentage in blood or bone marrow for a diagnosis of acute myeloid leukemia is:
WHO sets the threshold at 20% blasts (the older FAB system used 30%). AML with certain defining genetic changes, such as t(15;17) or t(8;21), can be diagnosed below 20%.
Which ABO group has the MOST H antigen on its red cells?
H is the precursor that A and B transferases convert. Group O cells have no transferase, so H is left unchanged. The order is O > A2 > B > A2B > A1 > A1B.
Red cells of a patient do not react with anti-A, anti-B or anti-H lectin (Ulex europaeus), and the plasma agglutinates all group O cells. The most likely phenotype is:
Bombay (Oh) people lack the H gene, so they cannot make H, A or B antigens. They make strong anti-H as well as anti-A and anti-B, and can only receive blood from another Bombay donor.
Why does an ABO-incompatible transfusion typically cause acute intravascular hemolysis?
Naturally occurring anti-A and anti-B are mostly IgM. IgM fixes complement efficiently through to the membrane attack complex, lysing red cells in the circulation and causing haemoglobinaemia, haemoglobinuria and possibly DIC.
An 85-year-old group O patient shows weak or no reactions with A1 and B cells in reverse typing. The best first step to resolve this is:
The elderly, newborns and people with low immunoglobulins may have weak ABO antibodies. Longer incubation at room temperature or 4 °C, with an autocontrol and O cells as controls, strengthens the reactions.
An AST/ALT ratio greater than 2 with raised GGT most suggests:
Alcohol damages mitochondria (rich in AST) and lowers ALT through pyridoxine deficiency, so AST exceeds ALT, often by more than 2:1. Viral hepatitis and fatty liver usually show ALT greater than AST.
A healthy 20-year-old has mild unconjugated hyperbilirubinemia that rises during fasting, with normal liver enzymes and no hemolysis. The most likely diagnosis is:
Gilbert syndrome is a common, harmless reduction in UDP-glucuronyl transferase activity. Unconjugated bilirubin rises mildly with fasting, illness or stress; Dubin-Johnson causes conjugated hyperbilirubinemia.
Sodium fluoride in the grey-top tube preserves glucose by:
Cells keep using glucose after collection, lowering it by about 5-7% per hour at room temperature. Fluoride inhibits enolase and slows this; potassium oxalate in the same tube is the anticoagulant.
A very mucoid, non-motile, lactose-fermenting, indole-negative, urease-positive rod from sputum is most likely:
The thick capsule makes K. pneumoniae mucoid; it is non-motile and indole negative. K. oxytoca is indole positive, Enterobacter is motile and E. coli is indole positive.
A beta-hemolytic streptococcus from a vaginal-rectal swab of a pregnant woman is CAMP positive and hippurate positive. It belongs to:
Group B streptococci give a positive CAMP test (arrowhead hemolysis with S. aureus) and hydrolyse hippurate. They are screened in pregnancy because they cause neonatal sepsis and meningitis.
Which feature of an amoebic trophozoite most reliably indicates Entamoeba histolytica rather than E. dispar on microscopy?
E. histolytica and E. dispar look identical, but only the invasive E. histolytica ingests red cells. Otherwise, antigen or PCR tests are needed to tell them apart.
Mild microcytic anemia, normal ferritin, RBC count 6.1 × 10^6/µL and HbA2 of 5.2% suggest:
A raised HbA2 (above about 3.5%) with microcytosis and a high red cell count is typical of beta-thalassemia minor. Normal ferritin argues against iron deficiency, which can lower HbA2.
Spherocytes, raised MCHC, a negative DAT and increased osmotic fragility in a patient with a family history of anemia suggest:
Inherited defects of membrane proteins such as spectrin or ankyrin make cells spherical and fragile in hypotonic saline. A negative DAT separates this from warm autoimmune hemolysis, which also shows spherocytes.
Which antibody is notorious for showing dosage, fading in storage and causing delayed hemolytic transfusion reactions?
Kidd antibodies often drop to undetectable levels and then rise quickly after re-exposure, causing delayed hemolysis. They bind complement and react more strongly with homozygous cells.
Which practice gives the best chance of detecting bacteremia in an adult?
Yield rises with the volume of blood cultured and the number of sets. Several sets also help tell true infection from skin contamination. Antibiotics given first reduce recovery.