Clinical Chemistry Flashcards

An LD isoenzyme 'flipped pattern' (LD1 greater than LD2) is most characteristic of which condition?

Answer: Myocardial infarction

Cardiac muscle and red cells are rich in LD1, so myocardial injury raises LD1 above LD2.

Which alkaline phosphatase isoenzyme is the most heat-stable when serum is heated at 56°C?

Answer: Placental

Placental ALP resists heat inactivation at 56°C, while bone ALP is the most heat-labile.

A serum protein electrophoresis shows beta-gamma bridging. This pattern is most suggestive of:

Answer: Hepatic cirrhosis

Polyclonal IgA rises in cirrhosis and fills in the zone between the beta and gamma bands.

Decreased albumin with a markedly increased alpha-2 globulin band on SPE is typical of:

Answer: Nephrotic syndrome

Small proteins like albumin are lost in urine, while large alpha-2 macroglobulin is kept and rises.

A patient has elevated alkaline phosphatase and a normal GGT. The most likely source of the ALP is:

Answer: Bone

GGT rises with hepatobiliary ALP but not with bone ALP, so a normal GGT points to bone.

Elevated serum amylase, normal lipase, and a low urine amylase in an asymptomatic patient most likely indicates:

Answer: Macroamylasemia

Amylase bound to immunoglobulin is too large to be filtered, so serum levels rise and urine levels fall.

Kinetic assays for ALT and AST typically monitor the change in absorbance of NADH at which wavelength?

Answer: 340 nm

NADH absorbs strongly at 340 nm and NAD+ does not, so oxidation of NADH is measured as a drop in absorbance.