Medical Laboratory Technician Clinical Chemistry Procedures Questions and Answers

Question 1

A patient's blood gas results are as follows: pH = 7.25, pCO2 = 60 mmHg, HCO3- = 24 mEq/L. How would you classify this acid-base disturbance?

Accepted Answer

Respiratory Acidosis

Answer

The pH is below the normal range (7.35-7.45), indicating acidosis. The pCO2 is elevated (normal range 35-45 mmHg), which is the respiratory component. The HCO3- is within the normal range (22-26 mEq/L). Therefore, the primary disturbance is respiratory acidosis, as the high level of CO2 (an acid) is not being compensated for by the kidneys (metabolic component).

Question 2

A physician orders a creatinine clearance test to evaluate a patient's kidney function. The following results are obtained:
- Serum creatinine: 1.5 mg/dL
- Urine creatinine: 120 mg/dL
- Urine volume: 1440 mL/24 hours
- Body Surface Area (BSA): 1.73 m²

Using the standard formula, what is the calculated creatinine clearance in mL/min?

Accepted Answer

80 mL/min

Answer

The formula for creatinine clearance is: (Urine Creatinine x Urine Volume) / (Serum Creatinine x Time in minutes). First, convert the 24-hour urine volume to mL/min: 1440 mL / 1440 min = 1 mL/min. Then, apply the formula: (120 mg/dL * 1 mL/min) / 1.5 mg/dL = 80 mL/min. Since the patient's BSA is the standard 1.73 m², no correction is needed.

Question 3

Which of the following cardiac markers is the most specific for myocardial infarction and remains elevated for the longest duration after the event?

Accepted Answer

Troponin I

Answer

Troponin I is a protein that is highly specific to cardiac muscle. Following a myocardial infarction (heart attack), its levels rise within 3-6 hours, peak at 12-24 hours, and can remain elevated for 7-14 days. CK-MB and myoglobin rise earlier but are less specific and return to normal more quickly. AST is an older, non-specific marker for cardiac damage.

Question 4

A laboratorian performs an ion-selective electrode (ISE) measurement for electrolytes. The technologist notices that the potassium result is critically high, but the patient has no symptoms of hyperkalemia. A visual inspection of the serum shows significant hemolysis. Which of the following is the most likely explanation for the discrepant result?

Accepted Answer

Intracellular potassium was released from lysed red blood cells

Answer

Potassium is primarily an intracellular cation. Its concentration inside red blood cells is significantly higher than in the plasma. When hemolysis (rupture of red blood cells) occurs, this intracellular potassium is released into the serum, causing a falsely elevated (pseudohyperkalemia) result that does not reflect the patient's true physiological state.

Question 5

A patient with a history of diabetes has a Hemoglobin A1c (HbA1c) level of 9.0%. This result reflects the patient's average blood glucose level over what period of time?

Accepted Answer

The past 2-3 months

Answer

Hemoglobin A1c is formed when glucose in the blood binds irreversibly to hemoglobin within red blood cells. The level of HbA1c is proportional to the average glucose concentration in the blood. Since the average lifespan of a red blood cell is about 120 days, the HbA1c test provides an integrated picture of blood glucose control over the preceding 2-3 months.

Medical Laboratory Technician Exam Practice Test

Medical Laboratory Technician Exam Practice Test

Medical Laboratory Technician Clinical Chemistry Procedures Questions and Answers