Clinical Assessment Methods Flashcards

An anion gap of 24 mmol/L in a patient with metabolic acidosis is most consistent with:

Answer: Diabetic ketoacidosis

DKA adds unmeasured anions (ketoacids), increasing the anion gap.

Calculated serum osmolality is 290 mOsm/kg and measured is 320 mOsm/kg. This osmolal gap most suggests:

Answer: Presence of an unmeasured osmole such as ethylene glycol or methanol

An osmolal gap >10 indicates unmeasured osmotically active substances like toxic alcohols.

A BUN-to-creatinine ratio greater than 20:1 with elevated BUN most suggests:

Answer: Prerenal azotemia

Reduced renal perfusion increases urea reabsorption more than creatinine.

Which marker is preferred for estimating GFR when muscle mass is abnormal, such as in amputees or the elderly?

Answer: Cystatin C

Cystatin C is produced by all nucleated cells at a constant rate and is independent of muscle mass.

An AST/ALT ratio greater than 2 is classically associated with:

Answer: Alcoholic liver disease

Alcohol-related injury typically produces AST more than twice ALT.

Which result best differentiates hepatic from bone origin of an elevated alkaline phosphatase?

Answer: Elevated GGT

GGT rises in hepatobiliary disease but not bone disease.

Hemoglobin A1c reflects average blood glucose over approximately what period?

Answer: 2–3 months

A1c reflects glycemia over the RBC lifespan, about 8–12 weeks.