MLT GlobeQCHP exam preparation (Qatar) – page 10
749 practice MCQs for the QCHP medical laboratory exam. Level: Intermediate.
In a bone marrow aspirate from a patient with immune thrombocytopenia, megakaryocytes are usually:
In ITP platelets are destroyed peripherally, so the marrow compensates with normal or increased megakaryocytes. Absent megakaryocytes suggest marrow failure such as aplastic anemia.
A woman has long-standing microcytic anemia, spoon-shaped nails and difficulty swallowing due to an esophageal web. This combination is known as:
Plummer-Vinson (Paterson-Kelly) syndrome is iron deficiency with koilonychia and a post-cricoid web. Imerslund-Gräsbeck syndrome is inherited selective vitamin B12 malabsorption.
Compared with a healthy adult, the red cells of a healthy term newborn have:
Newborn red cells are macrocytic, with MCV often above 100 fL, and Hb is higher than in adults. MCV falls to childhood levels over the first months.
A rural farm worker who walks barefoot has chronic microcytic hypochromic anemia and eosinophilia. The most likely parasitic cause is:
Hookworm larvae enter through skin, and adult worms cause chronic intestinal blood loss leading to iron deficiency, often with eosinophilia. Diphyllobothrium causes B12 deficiency, not iron deficiency.
Compared with a thin blood film, a thick film for malaria is mainly used to:
A thick film lyses red cells and concentrates a larger blood volume, so it is more sensitive for detecting parasites. Species identification and red cell changes need the thin film, where cells stay intact.
The term 'poikilocytosis' describes:
Poikilocytosis means abnormal shapes. Anisocytosis refers to size, polychromasia to bluish color, and rouleaux to stacking.
A drepanocyte is another name for a:
Drepanocyte comes from the Greek for sickle. A target cell is a codocyte, a teardrop cell is a dacrocyte and a burr cell is an echinocyte.
A 16-year-old boy has breathlessness, a mediastinal mass and WBC 150 × 10^9/L with blasts that are cytoplasmic CD3+, CD7+ and TdT+. The most likely diagnosis is:
T-ALL typically affects adolescent males with a high WBC and a thymic (anterior mediastinal) mass; cCD3 with TdT confirms immature T-lineage blasts. Hodgkin lymphoma also causes mediastinal masses but not circulating TdT+ blasts.
A urine sample from a suspected myeloma patient is tested for monoclonal free light chains. The recommended method is:
Electrophoresis with immunofixation identifies and types monoclonal light chains (Bence Jones protein). Dipstick protein pads mainly detect albumin and react poorly with light chains, and the classic heat test is insensitive.
Lymphoblasts in ALL often show coarse 'block' positivity with which cytochemical stain?
PAS stains glycogen, which may appear as coarse blocks in lymphoblasts (and in erythroid precursors in erythroid neoplasms). MPO and Sudan black B are markers of myeloid lineage.
The usual adult reference interval for the total white cell count is about:
Most adult WBC reference intervals are about 4.0–11.0 × 10^9/L (4000–11 000/µL); exact limits vary slightly by lab. 150–400 × 10^9/L is the platelet reference interval.
A WBC count is 8.0 × 10^9/L and monocytes are 15% on the differential. The absolute monocyte count and interpretation are:
Absolute count = 8.0 × 0.15 = 1.2 × 10^9/L. Adult monocytes are usually below about 1.0 × 10^9/L, so this is an absolute monocytosis.
In adult peripheral blood, which lymphocyte subset is normally the largest?
About 60–80% of circulating lymphocytes are T cells, 10–20% B cells and 5–15% NK cells. Plasma cells are normally absent from blood.
Which condition is a classic cause of reactive monocytosis?
Chronic infections such as TB, endocarditis and syphilis, recovery from neutropenia and inflammatory disease cause monocytosis. Corticosteroids lower monocyte counts.
Which cell normally makes up the largest percentage of leukocytes in adult blood?
In adults neutrophils are about 40–75% of leukocytes and lymphocytes about 20–40%. In young children lymphocytes may predominate.
Fresh tissue for a frozen section is usually attached to the cryostat chuck using:
OCT compound freezes to a firm support around the tissue and attaches it to the chuck, and it dissolves in water during staining. Paraffin cannot be used with unfixed frozen tissue.
Before H&E staining of a paraffin section, the first step is to:
Aqueous dyes cannot penetrate paraffin, so sections are dewaxed in xylene and brought through alcohols to water. Acid alcohol is used later as a differentiator.
In the Verhoeff–van Gieson stain, elastic fibers appear:
Verhoeff's iron hematoxylin stains elastic fibers and nuclei black. The van Gieson counterstain then colors collagen red and muscle or cytoplasm yellow.
Mast cell granules stained with toluidine blue appear purple-red, while the background stains blue. This property is called:
Metachromasia is staining in a different color from the dye itself, caused by stacking of dye molecules on dense anionic groups such as heparin. Birefringence is a polarization property.
Picric acid must be stored moistened with water because, when dry, it:
Dry picric acid (and its metal picrates) is shock-sensitive and explosive, so it is kept wet and away from metal lids. Its yellow color and fixing ability are not the concern.