MLT GlobeSCFHS exam preparation (Saudi Arabia) – page 29
749 practice MCQs for the SCFHS medical laboratory exam. Level: Intermediate.
A pregnant woman at 34 weeks with hypertension has schistocytes, high LDH, raised ALT and platelets of 60 × 10^9/L. The most likely diagnosis is:
HELLP means Hemolysis, Elevated Liver enzymes and Low Platelets, a severe form of preeclampsia. Gestational thrombocytopenia is mild with no hemolysis or liver damage.
A multiparous woman develops severe thrombocytopenia and purpura 8 days after a red cell transfusion. Which antibody is most often responsible?
Post-transfusion purpura usually occurs in HPA-1a–negative women previously sensitized by pregnancy; the antibody destroys transfused and the patient's own platelets. Anti-PF4/heparin causes HIT.
An adult has had immune thrombocytopenia for 14 months. By international terms, this is:
ITP is newly diagnosed up to 3 months, persistent from 3 to 12 months and chronic after 12 months. 'Secondary' refers to an underlying cause, not duration.
In the platelet response to ristocetin, platelets clump by:
Ristocetin makes VWF bind GP Ib, causing passive agglutination that also occurs with fixed platelets. That is why it stays normal in Glanzmann thrombasthenia and on aspirin.
On most impedance hematology analyzers, the hematocrit is not measured directly. It is calculated from:
Impedance analyzers measure RBC count and MCV (mean pulse height); Hct (%) = MCV (fL) × RBC (10^12/L) ÷ 10. The MCHC is then derived from Hb and this calculated Hct, not the other way round.
In a healthy term infant, the hemoglobin normally falls to its lowest point (physiological anemia of infancy) at about:
After birth, higher oxygen levels suppress erythropoietin, so Hb falls to a nadir of about 9.5–11 g/dL at around 2–3 months. It then rises as erythropoiesis restarts.
A woman taking an estrogen-containing oral contraceptive has a raised TIBC, normal ferritin and normal Hb. The most likely explanation is:
Estrogen (and pregnancy) increases transferrin production, raising TIBC without iron deficiency. Iron deficiency would lower ferritin, and hemochromatosis or inflammation lowers TIBC.
A man has a major bleed from a peptic ulcer. One hour later he is hypotensive, but his Hb is 14.0 g/dL (140 g/L). The best explanation is:
In acute bleeding, red cells and plasma are lost together, so Hb stays near normal at first. It falls over 24–72 hours as tissue fluid or IV fluid expands plasma volume.
An untransfused child with beta-thalassemia major would be expected to show which smear picture?
Severe ineffective erythropoiesis gives marked microcytic hypochromic poikilocytosis, target cells, basophilic stippling and numerous nucleated red cells. Isolated spherocytes or macrocytes do not fit.
Infected red cells are oval, slightly enlarged, with ragged (fimbriated) edges and coarse red dots (James dots). The species is most likely:
P. ovale typically makes the infected cell oval with fimbriated ends and Schüffner-type (James) dots. P. malariae does not enlarge or distort the cell.
In the sodium metabisulfite slide test for HbS, red cells sickle because the reagent:
Sodium metabisulfite is a reducing agent that deoxygenates hemoglobin under a sealed coverslip, allowing HbS to polymerize and cells to sickle. It does not lyse the cells.
Red cells in Plasmodium vivax infection are often enlarged mainly because this species:
P. vivax (and P. ovale) preferentially invade reticulocytes, which are larger than mature cells, and the infected cell enlarges further. P. falciparum infects cells of all ages without enlarging them.
Red cells stored for many weeks lose ATP. The typical shape change is:
ATP depletion in stored cells causes shape change to echinocytes and, with further membrane loss, spheroechinocytes and spherocytes. This storage lesion is partly reversible after transfusion.
In the WHO 5th edition, chronic myeloid leukemia is diagnosed as being in blast phase when blasts in blood or marrow reach at least:
Blast phase of CML is defined by ≥20% blasts in blood or marrow, an extramedullary blast proliferation, or increased lymphoblasts. The 10% level was used for the old accelerated phase, which WHO 5th edition no longer requires.
A 5-year-old with B-ALL has a blast karyotype of 55 chromosomes with extra copies of chromosomes 4, 10 and 21. This finding is:
High hyperdiploidy (51–65 chromosomes), often with gains of 4, 10 and 21, is one of the most common and most favorable cytogenetic groups in childhood B-ALL. Hypodiploidy (<44 chromosomes) is the unfavorable group.
Two days after induction chemotherapy for a high-count leukemia, which set of results suggests tumor lysis syndrome?
Rapid lysis of tumor cells releases potassium, phosphate and nucleic acids (converted to uric acid). Phosphate binds calcium, so calcium falls. The opposite pattern does not fit cell breakdown.
A glucose sample from a patient with WBC 250 × 10^9/L sat unseparated for 3 hours and reads 1.8 mmol/L (32 mg/dL). The patient has no symptoms. Likely cause:
Very high numbers of metabolically active cells keep using glucose after collection, giving a falsely low result. Rapid separation or a fluoride tube reduces this. Fluoride blocks glycolysis, so it would protect glucose, not lower it.
In the Revised International Staging System for multiple myeloma, which two serum markers are combined with high-risk cytogenetics and LDH?
Staging uses serum beta-2 microglobulin (tumor burden and renal function) and albumin, adding LDH and high-risk FISH in the revised system. Calcium and creatinine are CRAB criteria for diagnosis, not staging.
A boy with recurrent skin abscesses and liver abscesses with Staphylococcus and Aspergillus has neutrophils that show no fluorescence shift on the dihydrorhodamine (DHR) flow test. The disorder is:
The DHR test measures NADPH oxidase activity; absent respiratory burst confirms chronic granulomatous disease. MPO deficiency gives a normal DHR response and is usually mild.
After release from the marrow, neutrophils stay in the circulating blood for about:
Neutrophils have a blood half-life of about 7 hours before moving into tissues, where they live 1–2 days. 120 days is the red cell life span; 7–10 days is the platelet life span.