MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 33
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
Broad casts, several times wider than ordinary casts, are most significant because they indicate:
Broad casts form in widened distal or collecting tubules where flow is very slow, often in advanced chronic kidney disease, hence the old name 'renal failure casts'.
A pink precipitate ('brick dust') forms in a refrigerated acidic urine and obscures the sediment. What will dissolve it?
Amorphous urates form in cooled acid urine and dissolve when warmed to about 60 °C or on alkalinization. Amorphous phosphates, found in alkaline urine, dissolve in dilute acetic acid.
Large, flat, colourless plates with a notched corner are seen in urine of a patient with nephrotic syndrome. They are:
Cholesterol crystals are flat plates with notched corners, often seen with lipiduria in nephrotic syndrome. They are best seen in refrigerated samples.
Phase-contrast examination shows that most urinary red cells are small with blebs, ring forms and budding (acanthocytes). This mainly suggests:
Dysmorphic red cells, especially acanthocytes (G1 cells), are damaged as they pass through the glomerulus and tubules, pointing to glomerular disease. Lower tract bleeding gives mostly normal-shaped red cells.
When preparing urine sediment by a standardized method, a typical procedure is:
Standardized procedures centrifuge a fixed volume (about 10–15 mL) at around 400 RCF for 5 minutes so results are comparable. High forces can damage casts and cells.
A urine sample with low specific gravity (1.003) and pH 8.0 was left at room temperature for 4 hours. What is most likely to be underestimated on microscopy?
Casts dissolve in dilute, alkaline urine, and delay makes this worse. Bacteria multiply rather than decrease at room temperature.
A group A patient with a bowel infection shows a new weak reaction with anti-B. Which finding supports acquired B rather than true group AB?
In acquired B, bacterial deacetylase makes A-antigen GalNAc look like galactose; the patient's own anti-B does not recognise it. Acidified anti-B stops reacting, and secretor saliva contains A, not B, substance.
Red cells show typical mixed-field agglutination with anti-A and anti-A,B, and the saliva of this secretor contains A substance. The most likely A subgroup is:
A3 is characterised by mixed-field agglutination with anti-A and anti-A,B, and secretors have A in saliva. Ax cells usually react better with anti-A,B than anti-A and are not typically mixed-field.
Low-titer group O whole blood is used in trauma resuscitation mainly because:
Group O plasma does contain anti-A and anti-B, so units are selected for low titers to limit hemolysis when given to A, B or AB patients.
A technologist incubates reverse-typing tubes at 37 °C for 30 minutes before reading. The most likely effect is:
Anti-A and anti-B are mainly IgM and react best at room temperature or below. Warm incubation can weaken reactions and cause a false discrepancy.
For a neonate younger than 4 months, repeat ABO/D typing during the same hospital admission is:
Infants under 4 months rarely make new antibodies, so one ABO/D type per admission is enough. Reverse typing is not done because antibodies are maternal.
Some laboratories add group O reagent cells to reverse typing. A positive reaction with the O cells suggests:
Normal ABO antibodies do not react with O cells. Reaction points to a cold alloantibody, autoantibody or anti-H (e.g., Bombay).
Soluble ABH substances in the saliva of secretors are mainly:
In secretions ABH antigens are carried on glycoproteins (mucins). On red cells they are on both glycoproteins and glycolipids.
A group O patient receives group A apheresis platelets. Compared with group O platelets, a possible effect is:
Platelets carry A antigen, so the recipient's anti-A shortens their survival and can lower the increment. Anti-D formation depends on D, not ABO.
Chloroquine diphosphate treatment of DAT-positive red cells is used to:
Chloroquine dissociates IgG from red cells with little antigen damage, allowing typing with IAT reagents. It does not remove complement.
The antibody screen is negative, but the AHG crossmatch is incompatible with one of four units. The DAT on that unit is negative. The most likely cause is:
Screening cells rarely carry low-prevalence antigens, so such antibodies are found only by crossmatch. A high-prevalence antibody or autoantibody would react with the screen and most units.
An antibody to a high-prevalence antigen is identified, and no compatible blood is available locally. The best source of compatible donors is:
Siblings are the most likely to share a rare antigen-negative phenotype, and rare donor programs keep frozen rare units. Washing does not remove antigens.
Which elution method is commonly used to remove warm IgG autoantibodies from red cells?
Acid elution recovers IgG warm antibodies well. Heat and freeze–thaw methods are mainly used for ABO antibodies.
Whether a cold autoantibody causes hemolysis is best predicted by its:
An antibody that reacts at 30 °C or above can bind in peripheral circulation and cause hemolysis. A high 4 °C titer alone may be harmless.
Proteolytic enzymes enhance some antibody reactions mainly because they:
Removing sialic acid reduces zeta potential and exposes some antigens such as Rh and Kidd, so cells come closer together.