MLT GlobeQCHP exam preparation (Qatar) – page 6
749 practice MCQs for the QCHP medical laboratory exam. Level: Intermediate.
Polychromatic (bluish-grey) red cells on a Wright-stained smear correspond to which cells on a new methylene blue stain?
Polychromasia is due to residual ribosomal RNA taking up the basic dye; the same RNA forms the reticulum on supravital stain. Siderocytes contain iron granules, not diffuse RNA.
Rouleaux on a peripheral smear should be assessed only in the thin area where red cells just touch because:
In thick areas cells overlap and can look like coin stacks even in normal blood, giving a false impression of rouleaux. True rouleaux persist in the proper reading area.
When making a wedge blood film, which change produces a THICKER smear?
A steeper spreader angle gives a shorter, thicker film; a lower angle gives a longer, thinner one. A small drop or low hematocrit tends to produce thinner films.
A patient with chronic kidney disease has many red cells with 10–30 short, evenly spaced projections on a fresh smear. These cells are called:
Echinocytes, also called burr cells, have short regular projections and are seen in uremia as well as in storage artefact. Acanthocytes have fewer, irregular projections.
Crescent- or banana-shaped gametocytes on a thin blood film are characteristic of:
P. falciparum gametocytes are crescent-shaped, while the other species have round gametocytes. P. vivax shows enlarged cells with Schüffner dots instead.
A marrow cell has a round nucleus with visible nucleoli, basophilic cytoplasm and many large reddish-purple granules, with a clear Golgi zone. It is a:
Abundant large primary azurophilic granules with nucleoli define the promyelocyte. Myeloblasts have few or no granules.
A granulocyte precursor with a kidney-bean (indented) nucleus, condensed chromatin, no nucleoli and pink secondary granules is a:
The metamyelocyte has an indented, kidney-shaped nucleus with indentation less than half the nuclear width. A myelocyte nucleus is round or oval.
A 10-year-old from a rural area has abdominal pain and an eosinophil count of 3.2 × 10^9/L. The most likely cause is:
Tissue-invasive helminths are the leading cause of eosinophilia worldwide. Acute bacterial infection and corticosteroids usually lower eosinophils.
Which feature best identifies a myeloblast on a Wright-stained smear?
Myeloblasts have fine chromatin, 2–5 nucleoli, a high N:C ratio and few or no granules. A perinuclear hof with clumped chromatin describes a plasma cell.
A small drumstick-shaped nuclear appendage seen on a few neutrophils represents:
The neutrophil drumstick is the inactivated X chromosome, seen in females. Howell-Jolly bodies are nuclear remnants in red cells.
A conventional Pap smear was left to air-dry for several minutes before being placed in 95% ethanol. What change is expected?
Pap staining requires immediate wet fixation. Air-drying causes nuclei to enlarge and stain pale, obscuring chromatin detail and making interpretation difficult.
What is the main advantage of preparing a cell block from residual FNA material or fluid sediment?
A cell block concentrates cells, which are processed and embedded like tissue. Multiple sections can then be cut for immunohistochemistry, special stains and molecular tests.
A fixative containing picric acid, formaldehyde and acetic acid, often used for testis and GI biopsies, is:
Bouin's solution contains picric acid, formaldehyde and acetic acid and gives crisp nuclear detail. Zenker's is a mercuric chloride fixative.
What is the usual section thickness for routine paraffin sections stained with H&E?
Routine paraffin sections are cut at about 3–5 µm. Semithin plastic sections for EM are 0.5–1 µm, and thick sections are used for special purposes such as some nerve work.
A patient on procainamide develops arthralgia and a positive ANA. Which antibody is most typical of this condition?
Drug-induced lupus (procainamide, hydralazine, isoniazid) is characterised by anti-histone antibodies; anti-dsDNA and anti-Sm are usually absent. Symptoms resolve after the drug is stopped.
Anti-Scl-70 (topoisomerase I) antibody is most associated with:
Anti-Scl-70 is specific for diffuse cutaneous systemic sclerosis and is linked to interstitial lung disease. Anti-centromere is more typical of the limited form.
MHC class I molecules present peptide antigens to which cells?
MHC class I, found on all nucleated cells, presents intracellular (endogenous) peptides to CD8+ cytotoxic T cells. MHC class II presents exogenous peptides to CD4+ T cells.
Which complement component is shared by all three complement pathways and is the point where they converge?
The classical, lectin and alternative pathways all generate a C3 convertase that cleaves C3. C1q, C2 and C4 are used by the classical (and lectin, for C2/C4) pathways but not the alternative pathway.
The primary lymphoid organ where T cells mature and undergo positive and negative selection is the:
T-cell precursors from the bone marrow mature in the thymus, where positive selection (MHC recognition) and negative selection (self-tolerance) occur. Spleen and lymph nodes are secondary lymphoid organs.
Compared with a primary antibody response, a secondary (anamnestic) response shows:
Memory B cells respond faster on re-exposure, producing higher titres of mainly IgG with increased affinity (affinity maturation). A primary response has a longer lag and is dominated by IgM.