MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 37
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
Clear fluid drips from the nose after a head injury. Which protein confirms that the fluid is CSF?
Beta-2 transferrin (asialotransferrin) is formed in the CNS by neuraminidase and is found in CSF and perilymph but not in nasal secretions or serum. It is detected by electrophoresis with immunofixation.
Compared with ESR, C-reactive protein is better for monitoring an acute infection because CRP:
CRP is made by the liver under IL-6 stimulation, rises within 6–8 hours and has a half-life of about 19 hours, so it falls quickly with recovery. ESR changes slowly and is affected by anemia and red cell shape.
A hemodialysis patient has pre-dialysis urea 25 mmol/L and post-dialysis urea 8 mmol/L. What is the urea reduction ratio (URR)?
URR = (pre − post)/pre × 100 = (25 − 8)/25 × 100 = 68%. A URR of at least 65% is commonly used as a target for adequate dialysis. 32% is the post/pre ratio, not the reduction.
Urea clearance is a poor measure of GFR mainly because urea is:
Urea is freely filtered but 40–60% diffuses back from the tubules, more when urine flow is low, so urea clearance underestimates GFR. Secretion is the problem with creatinine, not urea.
A workplace urine screen is positive for opiates. Confirmation shows morphine only, at a low level, and the person reports eating poppy seed bread. The correct interpretation is:
Poppy seeds contain morphine and codeine and can give a positive opiate result. Heroin use is proven by its specific metabolite 6-acetylmorphine, which is not produced by poppy seeds.
In the International Staging System for multiple myeloma, which two serum tests are used together?
ISS stage is based on serum beta-2 microglobulin (reflecting tumor burden and kidney function) and albumin; the revised ISS adds LDH and cytogenetics. Calcium and creatinine assess organ damage.
A patient with episodic headache, sweating and palpitations has very high blood pressure. The preferred first biochemical test is:
Plasma free (or urine fractionated) metanephrines are the most sensitive screening tests for pheochromocytoma and paraganglioma. Urine 5-HIAA is used for carcinoid tumors.
Which marker is combined with CA-125 in the ROMA algorithm to assess the risk of ovarian malignancy in a pelvic mass?
ROMA combines CA-125 and HE4 with menopausal status. HE4 is less often raised by benign conditions such as endometriosis, improving specificity over CA-125 alone.
A patient with a gallstone blocking the common bile duct and cholangitis has a CA 19-9 of 900 U/mL. After the stone is removed, CA 19-9 becomes normal. The raised value was due to:
CA 19-9 is cleared through bile, and biliary obstruction or inflammation can raise it greatly without cancer. Normalization after relieving obstruction supports a benign cause.
A child has prolonged fever, splenomegaly, pancytopenia and a serum ferritin of 25,000 µg/L (ng/mL). Which condition is most strongly suggested?
Extremely high ferritin with fever, cytopenias and splenomegaly is typical of HLH, caused by uncontrolled macrophage activation. Iron deficiency gives a low ferritin.
When iron supply to developing red cells is inadequate, which substance increases in red cells?
Without enough iron, ferrochelatase inserts zinc into protoporphyrin, so zinc protoporphyrin rises in iron deficiency (and in lead poisoning). Hemosiderin is a storage form that falls in iron deficiency.
Which hematology analyser parameter gives an early measure of iron available for new red cells over the past few days?
Reticulocytes circulate for only 1–2 days, so their hemoglobin content reflects current iron supply to the marrow. MCHC changes late because mature cells live about 120 days.
Serum iron is 20 µmol/L and unsaturated iron-binding capacity (UIBC) is 55 µmol/L. What is the transferrin saturation?
TIBC = serum iron + UIBC = 20 + 55 = 75 µmol/L. Saturation = 20 ÷ 75 × 100 = 26.7%, about 27%. Dividing iron by UIBC instead gives 36%.
An impedance WBC histogram shows a peak starting at the lower threshold (about 35 fL), and the analyzer flags the region. The most likely cause is:
Nucleated RBC nuclei and large platelet clumps are about the size of small lymphocytes or smaller and create a signal at the lower edge of the WBC histogram. A smear review should confirm the cause.
In multicolor flow cytometry, compensation is applied to correct for:
Emission spectra overlap, so part of one dye's light is detected in another channel; compensation subtracts this spillover. Fc receptor binding is reduced by blocking, not compensation.
According to ICSH guidance, an EDTA sample for a Westergren-type ESR kept at room temperature should be tested within about:
ESR rises less over time as cells become more spherical, so room-temperature EDTA samples should be tested within about 4 hours (longer only if refrigerated and brought back to room temperature).
During a run, an analyzer shows falsely low counts and an abnormal pulse flag. Partial blockage of the counting aperture is suspected. The best first action is:
A partially blocked aperture reduces flow and distorts pulses, so counts and sizes are unreliable. The aperture must be cleaned, performance checked with controls, and affected samples rerun.
Red cell osmotic fragility is typically DECREASED in which condition?
Target cells have extra membrane relative to volume, so they can swell more before lysis and resist hypotonic saline. The other conditions produce spherocytes, which lyse easily.
A patient has mild chronic hemolysis with Heinz bodies, normal G6PD activity and a positive isopropanol precipitation test. The most likely cause is:
Unstable hemoglobins denature and precipitate in isopropanol or on heating, forming Heinz bodies. With normal G6PD activity, the Heinz bodies are not from an enzyme defect; PK deficiency does not cause Heinz bodies.
Flow cytometric sizing of a PNH clone is most reliable on neutrophils and monocytes rather than red cells because:
Complement destroys PNH red cells and transfused normal cells dilute the rest, so red cells underestimate the clone. Granulocytes and monocytes, tested with FLAER and CD24/CD14, give a truer clone size.