Laboratory Science Clinical Chemistry 3

Question 1

What is the clinical significance of a PSA (prostate-specific antigen) level greater than 10 ng/mL?

Accepted Answer

Highly suspicious for prostate cancer, requiring further workup

Answer

PSA >10 ng/mL significantly increases the probability of prostate cancer and warrants biopsy; however, PSA elevation is not diagnostic alone (also elevated in BPH and prostatitis).

Question 2

Which hormone is measured by the beta-hCG test and why is it clinically useful?

Accepted Answer

Beta-human chorionic gonadotropin — for pregnancy detection and trophoblastic tumor monitoring

Answer

Beta-hCG is produced by trophoblastic cells; it's used for early pregnancy detection, monitoring ectopic pregnancy, and as a tumor marker for gestational trophoblastic disease and germ cell tumors.

Question 3

What is the clinical significance of an elevated D-dimer test?

Accepted Answer

Indicates fibrinolytic activity; elevated in DVT/PE but not specific — requires imaging confirmation

Answer

D-dimer is a fibrin degradation product; elevated levels indicate ongoing clot formation and lysis (high sensitivity for DVT/PE) but poor specificity — imaging is required to confirm.

Question 4

Which test is used to screen for phenylketonuria (PKU) in newborns?

Accepted Answer

Guthrie bacterial inhibition assay or tandem mass spectrometry for phenylalanine

Answer

Newborn PKU screening measures phenylalanine levels in dried blood spots via Guthrie assay or LC-MS/MS; elevated phenylalanine confirms inability to metabolize this amino acid.

Question 5

What does the osmolal gap indicate when elevated?

Accepted Answer

Presence of unmeasured osmoles such as ethanol, methanol, or ethylene glycol

Answer

Osmolal gap = measured osmolality − calculated osmolality; a gap >10 mOsm/kg suggests unmeasured osmoles like alcohols (ethanol, methanol, isopropanol, ethylene glycol) in the blood.

Laboratory Science Practice Test

Laboratory Science Practice Test

Laboratory Science Clinical Chemistry 3