MLT GlobeASCP exam preparation (USA · MLS / MLT) – page 8
1200 practice MCQs for the ASCP medical laboratory exam. Level: Advanced.
Where is most of the body's magnesium stored?
About 50–60% of body magnesium is in bone and most of the rest is inside soft tissue cells; only about 1% is extracellular. This is why serum Mg can be normal while body stores are low.
What is the approximate reference interval for serum osmolality in adults?
Serum osmolality is normally about 275–295 mOsm/kg, controlled by thirst and ADH. Values above 300 mOsm/kg indicate hypertonicity.
Which property of a solution is NOT a colligative property?
Colligative properties depend only on the number of dissolved particles: freezing point depression, boiling point rise, vapor pressure lowering and osmotic pressure. Viscosity depends on particle size and shape.
Blood for electrolytes was collected in a sodium heparin tube. Which result will be falsely affected?
Sodium heparin adds sodium to the sample, so sodium is falsely increased. Lithium heparin is the preferred heparin salt for electrolyte testing.
In a normal early intrauterine pregnancy, serum hCG approximately doubles every:
In early viable intrauterine pregnancy, hCG roughly doubles every 48 hours (about 48-72 h) during the first weeks. The rate of rise slows after about 6-7 weeks, and hCG peaks at about 8-10 weeks before falling. A rise that is too slow may suggest ectopic or failing pregnancy.
How do steroid hormones such as cortisol mainly act on target cells?
Steroids are lipid-soluble, cross the membrane and bind cytoplasmic or nuclear receptors that act as transcription factors. Peptide hormones use cell-surface receptors and second messengers.
In the IUBMB enzyme classification, ALT and AST belong to which class?
Aminotransferases move an amino group from an amino acid to a keto acid, so they are transferases (EC 2). Dehydrogenases such as LD are oxidoreductases (EC 1).
Besides CK, which serum enzyme is used as a marker of skeletal muscle disease?
Aldolase, a glycolytic enzyme, is high in skeletal muscle and rises in muscular dystrophies and myositis. GGT and 5′-nucleotidase are markers of hepatobiliary disease.
On agarose lipoprotein electrophoresis, HDL migrates in which position?
HDL moves fastest toward the anode, in the alpha position. LDL is in the beta band, VLDL in pre-beta, and chylomicrons stay at the origin.
A neonatal bilirubin sample was left uncovered on a sunny bench for 2 hours before testing. The result will most likely be:
Bilirubin is photo-oxidized by light and can fall by up to about 50% per hour in bright light. Samples should be protected with amber tubes or foil.
A total bilirubin of 3.0 mg/dL is equal to about how many µmol/L? (1 mg/dL = 17.1 µmol/L)
3.0 × 17.1 = 51.3 µmol/L. Dividing instead of multiplying gives the wrong value of about 0.18.
A patient with severe vomiting has total protein 8.6 g/dL (86 g/L) and albumin 5.4 g/dL (54 g/L); both return to normal after IV fluids. The cause of the high values was:
Loss of plasma water concentrates all proteins, so total protein and albumin rise together and correct with rehydration. True hyperalbuminemia from disease almost never occurs.
Which measurement is most useful to check whether a 24-hour urine collection is complete?
Creatinine excretion is fairly constant for a person and depends on muscle mass, so a total far below the expected amount suggests under-collection. Volume varies with fluid intake and cannot confirm completeness.
Therapeutic drug monitoring is most useful for drugs that have:
TDM is valuable when toxic and effective concentrations are close and patients handle the drug differently. Drugs with a wide margin or easily measured effects rarely need routine level monitoring.
For a patient taking oral digoxin once daily, when should blood be drawn for a digoxin level?
Digoxin distributes slowly from blood to tissue. Samples taken earlier than 6–8 hours after the dose show falsely high levels that do not reflect tissue (effect-site) concentration.
Most hCG immunoassays use an antibody against the beta subunit because the alpha subunit:
hCG, LH, FSH and TSH share an almost identical alpha subunit; the beta subunit gives each hormone its specificity. Targeting beta-hCG avoids cross-reaction with the other glycoprotein hormones.
Which test is traditionally regarded as the gold standard for assessing body iron stores?
Perls Prussian blue staining of marrow directly shows storage iron in macrophages and sideroblasts. It is invasive, so serum ferritin is used in routine practice. Serum iron varies daily.
Automated reticulocyte counting identifies reticulocytes by:
Fluorescent or absorbing dyes bind RNA, and the amount of signal separates reticulocytes from mature cells and grades their maturity (IRF). Impedance alone cannot detect RNA.
The blue laser used in most clinical flow cytometers to excite FITC and PE emits light at about:
A 488 nm blue laser excites FITC and PE and is standard in clinical instruments. A 633–640 nm red laser is used for dyes such as APC.
In impedance analyzers, platelets are separated from red cells counted in the same aperture by:
Platelets give small pulses (about 2–20 fL) and red cells larger pulses (about 36 fL and above), so volume thresholds separate them. Fluorescent staining is used for reticulocytes and some optical platelet methods.