MLPAO Clinical Chemistry Advanced Concepts 2

Question 1

What is the primary advantage of using enzymatic creatinine assays over the Jaffe method?

Accepted Answer

Greater specificity with fewer interferences

Answer

Enzymatic creatinine assays offer greater specificity than the Jaffe method because they are less susceptible to interference from non-creatinine chromogens such as glucose, acetoacetate, cephalosporins, and bilirubin. This is particularly important in neonatal and pediatric samples.

Question 2

Which calculation is used to estimate glomerular filtration rate (eGFR) in Canadian clinical practice?

Accepted Answer

CKD-EPI equation

Answer

The CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation is recommended for estimating GFR in Canadian clinical practice. It uses serum creatinine, age, and sex and is more accurate than the older MDRD equation, particularly at higher GFR values.

Question 3

What causes a delta check failure in the clinical chemistry laboratory?

Accepted Answer

A significant difference between a patient's current and previous result

Answer

A delta check compares a patient's current test result with their previous result and flags significant changes that may indicate specimen misidentification, sample mix-up, or acute clinical change. The acceptable delta varies by analyte and is typically expressed as a percentage or absolute change.

Question 4

Which hormone is measured using a stimulation test with cosyntropin (synthetic ACTH)?

Accepted Answer

Cortisol

Answer

The cosyntropin stimulation test measures cortisol response to synthetic ACTH to assess adrenal gland function. A normal response shows cortisol rising above 500 nmol/L, while an inadequate response suggests primary adrenal insufficiency (Addison disease).

Question 5

What is the principle of the ion-selective electrode used for measuring ionized calcium?

Accepted Answer

Potentiometry using a calcium-selective membrane

Answer

Ionized calcium is measured by potentiometry using an electrode with a calcium-selective membrane (typically containing a calcium-selective ionophore). The electrode generates a voltage proportional to the logarithm of ionized calcium activity in the specimen.

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO Clinical Chemistry Advanced Concepts 2