MLT GlobeSCFHS exam preparation (Saudi Arabia)
749 practice MCQs for the SCFHS medical laboratory exam. Level: Intermediate.
Subject mix: Hematology 20%, Chemistry 20%, Blood Banking 20%, Immunology & Serology 15%, Bacteriology 13%, Histo & Cyto Techniques 3%, Parasitology 3%, Histopathology 2%, Virology 2%, Mycology 2%
A surgeon needs an intraoperative diagnosis within minutes. Which instrument cuts the tissue?
A cryostat is a microtome in a refrigerated cabinet that sections frozen, unprocessed tissue quickly.
Neutral lipids are to be demonstrated with Oil Red O. How should the tissue be sectioned?
Alcohols and clearing agents in paraffin and celloidin processing dissolve lipids, so frozen sections are used.
Before IHC, paraffin sections are dewaxed by immersion in:
Xylene dissolves paraffin; alcohol then removes the xylene before rehydration and retrieval.
Nissl substance (clumps of rough ER) is characteristic of which cells?
Nissl bodies are basophilic rough ER in neuronal cell bodies, reflecting intense protein synthesis.
Mesothelium forms the surface lining of which layer of the gut wall?
Mesothelium is simple squamous epithelium lining serous membranes such as peritoneum, pleura and pericardium.
At what stage should bone be decalcified?
Tissue must be fully fixed first; decalcifying unfixed tissue causes severe damage. Surface decalcification of a block is only an occasional supplement.
How much water is added to 300 mL of 37–40% formaldehyde to prepare 10% formalin?
10% formalin is 1 part stock to 9 parts water, so 300 × 9 = 2700 mL water (3000 mL total).
Which inclusion, when seen in blasts on a peripheral smear, most strongly points to a myeloid rather than a lymphoid acute leukemia?
Auer rods are rod-shaped fusions of primary (azurophilic) granules containing myeloperoxidase. They are found only in myeloid blasts, so their presence rules in AML and effectively rules out ALL.
The most common leukemia in children is:
B-ALL makes up about three-quarters of childhood leukemias, with a peak at 2 to 5 years. CLL is the most common leukemia in older adults in Western countries.
Na 140 mmol/L, Cl 100 mmol/L and HCO3 10 mmol/L. What is the anion gap (without K)?
Anion gap = Na - (Cl + HCO3) = 140 - (100 + 10) = 30 mmol/L. This is high (usual range about 8-16) and suggests a high anion gap acidosis such as DKA, lactic acidosis, renal failure or poisoning.
Which form of serum calcium is physiologically active?
About 45-50% of serum calcium is ionized and biologically active; roughly 40% is bound to albumin and the rest to anions. Ionized calcium is not affected by albumin levels, unlike total calcium.
Which pattern is typical of hemolytic (prehepatic) jaundice?
Excess heme breakdown floods the liver with unconjugated bilirubin, which is not water soluble and does not enter urine. More bilirubin reaches the gut, so urobilinogen rises.
According to ADA criteria, which result is diagnostic of diabetes mellitus (confirmed on repeat testing)?
ADA criteria are HbA1c 6.5% or more, fasting glucose 126 mg/dL (7.0 mmol/L) or more, 2-hour OGTT glucose 200 mg/dL or more, or random glucose 200 mg/dL or more with symptoms.
A light-blue (3.2% sodium citrate) tube is only half filled. What is the effect on the PT and aPTT?
The correct ratio is 9 parts blood to 1 part citrate. With too little blood, excess citrate binds the calcium added in the test, so clotting times come out falsely long.
Many schistocytes with thrombocytopenia most suggest:
Schistocytes are red cell fragments cut by fibrin strands in small vessels. With low platelets they point to a thrombotic microangiopathy, which in TTP is an emergency.
A teenager with fever, sore throat and lymphadenopathy has many large lymphocytes with abundant blue cytoplasm that 'scallops' around red cells. The best next test is:
These are reactive (Downey) lymphocytes, typical of infectious mononucleosis caused by EBV. A heterophile antibody test or EBV serology confirms it.
For Kirby-Bauer disk diffusion, the inoculum is adjusted to a turbidity of:
CLSI disk diffusion uses a 0.5 McFarland suspension swabbed onto Mueller-Hinton agar. A heavier inoculum gives falsely small zones (false resistance); a lighter one gives false susceptibility.
A patient is positive for HBsAg and IgM anti-HBc, and negative for anti-HBs. This indicates:
HBsAg shows current infection and IgM anti-HBc shows it is recent. Vaccination produces anti-HBs only, and past infection shows anti-HBs with total anti-HBc.
A patient develops fever, chills and back pain 10 minutes into a red cell transfusion. The FIRST action is to:
Stop the transfusion at once, keep venous access with saline, check the patient and unit identification, and send post-transfusion samples and the bag to the blood bank for a DAT and repeat typing.
Naturally occurring anti-A and anti-B in a group A or group B adult are mainly of which class, and react best at what temperature?
ABO antibodies in group A and B people are mostly IgM, agglutinating saline-suspended cells at room temperature or colder, although they can also react and activate complement at 37 °C.