MLPAO Clinical Chemistry Laboratory Practice 2

Question 1

What is the purpose of the Levey-Jennings chart in quality control?

Accepted Answer

To plot QC results over time and visually detect trends, shifts, and outliers

Answer

A Levey-Jennings chart plots QC values over time with the mean and standard deviation limits displayed. This visual tool allows laboratory professionals to identify patterns such as shifts (sudden change in mean), trends (gradual change), and outliers that indicate analytical problems.

Question 2

Which type of error is characterized by results that are consistently higher or lower than the true value?

Accepted Answer

Systematic error (bias)

Answer

Systematic error (bias) produces results that are consistently displaced in one direction from the true value. It can be constant (same magnitude regardless of concentration) or proportional (error changes with concentration). Causes include calibration errors, reagent deterioration, and matrix effects.

Question 3

What is the clinical significance of measuring serum haptoglobin?

Accepted Answer

Confirming intravascular hemolysis

Answer

Serum haptoglobin binds free hemoglobin released during intravascular hemolysis. The haptoglobin-hemoglobin complex is cleared by the reticuloendothelial system, resulting in decreased or absent serum haptoglobin. It is a sensitive marker for intravascular hemolysis when combined with elevated LDH and indirect bilirubin.

Question 4

Which condition would cause an elevated anion gap metabolic acidosis?

Accepted Answer

Diabetic ketoacidosis

Answer

Diabetic ketoacidosis (DKA) causes elevated anion gap metabolic acidosis due to accumulation of ketoacids (acetoacetate and beta-hydroxybutyrate). The mnemonic MUDPILES helps remember causes: Methanol, Uremia, DKA, Propylene glycol, Isoniazid/Iron, Lactic acidosis, Ethylene glycol, Salicylates.

Question 5

What is the role of internal standard in mass spectrometry-based clinical chemistry methods?

Accepted Answer

To compensate for matrix effects and variations in ionization efficiency

Answer

Internal standards (typically isotope-labeled analogs of the target analyte) are added to specimens before extraction to compensate for variations in sample preparation, matrix effects, and ionization efficiency. The ratio of analyte signal to internal standard signal provides accurate quantitation.

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO - Medical Laboratory Professionals Association of Ontario Practice Test

MLPAO Clinical Chemistry Laboratory Practice 2