MLPAO Clinical Chemistry Fundamentals

Question 1

Which enzyme is considered the most specific marker for myocardial infarction when measured in serum?

Accepted Answer

Troponin I

Answer

Troponin I is the most specific cardiac biomarker for myocardial infarction. While CK-MB was historically used, troponin I is found almost exclusively in cardiac muscle and remains elevated for a longer period, making it the gold standard for MI diagnosis.

Question 2

What is the primary buffer system in human blood plasma?

Accepted Answer

Bicarbonate-carbonic acid buffer system

Answer

The bicarbonate-carbonic acid buffer system is the primary buffer in blood plasma, maintaining pH between 7.35 and 7.45. This system is regulated by both the lungs (CO2 excretion) and kidneys (bicarbonate reabsorption), making it highly effective at maintaining acid-base balance.

Question 3

A patient presents with a serum sodium of 128 mmol/L. Which condition is this most consistent with?

Accepted Answer

Hyponatremia

Answer

A serum sodium of 128 mmol/L is below the normal reference range of 136-145 mmol/L, indicating hyponatremia. This condition can result from excessive water retention, sodium loss, or conditions such as SIADH, and may present with neurological symptoms.

Question 4

Which method is most commonly used for measuring serum glucose in clinical chemistry analyzers?

Accepted Answer

Hexokinase method

Answer

The hexokinase method is the reference method for glucose measurement. It uses hexokinase to phosphorylate glucose to glucose-6-phosphate, which is then oxidized by glucose-6-phosphate dehydrogenase with production of NADPH, measured spectrophotometrically.

Question 5

What does an elevated serum creatinine level primarily indicate?

Accepted Answer

Decreased glomerular filtration rate

Answer

Elevated serum creatinine primarily indicates decreased glomerular filtration rate (GFR) and impaired kidney function. Creatinine is a byproduct of muscle metabolism that is freely filtered by the glomerulus and not significantly reabsorbed, making it a useful marker for renal function.

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO Clinical Chemistry Fundamentals