MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 32
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
A child with pica and a puppy at home has eosinophilia, hepatomegaly and a retinal lesion. No eggs are found in stool. Diagnosis is best made by:
Visceral and ocular larva migrans from Toxocara do not produce eggs in human stool because larvae do not mature. Serology supports the diagnosis.
A fourth-generation HIV-1/2 antigen/antibody immunoassay is reactive. What is the next step in the recommended algorithm?
The current CDC algorithm follows a reactive screen with an HIV-1/HIV-2 differentiation assay. Western blot is no longer used as the confirmatory test.
A rapid influenza antigen test is negative in a patient with typical symptoms during flu season. What is the best interpretation?
Rapid antigen tests have high specificity but limited sensitivity. A negative result in a likely case should be confirmed by a molecular test.
Which laboratory change in dengue warns of plasma leakage and possible severe disease?
Plasma leakage concentrates the blood, so hematocrit rises while platelets fall quickly. WHO lists this combination as a warning sign.
After hepatitis B vaccination, which anti-HBs level is generally considered protective?
An anti-HBs level of 10 mIU/mL or more after the vaccine series shows a protective response. Healthcare workers below this may need revaccination.
An HIV-positive patient has chronic headache. Which CSF test is most sensitive for cryptococcal meningitis?
Cryptococcal antigen tests (latex agglutination or lateral flow) are more sensitive than India ink, which shows encapsulated yeast in only some cases. Gram stain is poor for Cryptococcus.
Increased CSF myelin basic protein is mainly a marker of:
Myelin basic protein is released when myelin is damaged, as in multiple sclerosis relapses or other demyelinating injury. It does not show where IgG is made.
CSF arrives in the laboratory at night. How should the microbiology tube be stored if it cannot be processed immediately?
Microbiology CSF is kept at room temperature because fastidious organisms such as Neisseria meningitidis and Haemophilus influenzae die in the cold. Chemistry tubes may be frozen and hematology tubes refrigerated.
Synovial fluid from an elderly patient's knee shows rhomboid, weakly birefringent crystals that are blue when parallel to the slow axis of the compensator. The diagnosis is:
CPPD crystals are rhomboid or rod-shaped with weak positive birefringence (blue when parallel). They are typical of pseudogout, often in the knee of older people.
A synovial fluid is cloudy yellow-green with WBC 85,000/µL (95% neutrophils) and glucose much lower than blood glucose. The most likely classification is:
Very high WBC counts (usually above 50,000/µL) with mostly neutrophils and low glucose indicate septic arthritis; Gram stain and culture are urgent. Noninflammatory fluid has fewer than 2000 WBC/µL.
Pleural fluid protein is 3.5 g/dL and serum protein is 6.0 g/dL. Using Light's criteria (protein ratio >0.5), the fluid is:
Ratio = 3.5 ÷ 6.0 = 0.58, which is above 0.5, so the fluid is an exudate. Only one Light's criterion needs to be met.
A milky pleural fluid after chest trauma has triglyceride 250 mg/dL (2.8 mmol/L). This fluid is most likely:
Triglyceride above 110 mg/dL (1.24 mmol/L) and chylomicrons indicate chylous effusion from thoracic duct damage. Pseudochylous fluid is rich in cholesterol with low triglyceride.
In the eosin–nigrosin vitality test, which appearance indicates a dead sperm?
Dead sperm have damaged membranes and take up eosin, so the head stains pink-red; live sperm exclude the dye and appear white against the dark nigrosin background.
A urine positive with Clinitest (copper reduction) but negative with the reagent strip glucose pad most likely contains:
Copper reduction detects all reducing sugars, while the strip is specific for glucose. This pattern in an infant suggests galactosaemia and needs follow-up.
The reagent strip ketone pad (sodium nitroprusside) detects mainly:
Nitroprusside reacts strongly with acetoacetic acid, weakly with acetone (if glycine is present) and not at all with beta-hydroxybutyrate, the main ketone in diabetic ketoacidosis.
A positive blood pad with a uniform (non-speckled) colour, a clear red urine after centrifugation, and no red cells on microscopy is most consistent with:
Free hemoglobin or myoglobin gives uniform pad colour and red supernatant without intact RBCs. Intact RBCs give a speckled pattern and settle on centrifugation.
A patient with obstructive (post-hepatic) jaundice would most likely show which urine pattern?
Conjugated bilirubin enters urine, but bile cannot reach the intestine, so urobilinogen formation falls. Hemolytic jaundice gives negative bilirubin with high urobilinogen.
The urine bilirubin pad is based on:
Bilirubin couples with a diazonium salt in acid to form a coloured azodye. Ehrlich's reagent is used for urobilinogen on some strips.
The leukocyte esterase pad detects esterase from which cells?
Esterases are present in neutrophils, eosinophils, basophils and monocytes but not lymphocytes. The test detects intact and lysed granulocytes.
How is a mucus thread best distinguished from a hyaline cast in urine sediment?
Hyaline casts have parallel sides and rounded ends reflecting the tubule shape; mucus forms long, wavy, irregular strands. Both have low refractive index, so shape is the key feature.