Free Medical Laboratory Technician Clinical Chemistry Procedures Questions and Answers — Questions and Answers
Question 1: A patient sample is received in the lab with a milky, turbid appearance. This characteristic, known as lipemia, is most likely to interfere with which of the following?
- Spectrophotometric assays (Correct answer)
- Direct ion-selective electrode (ISE) measurements
- Immunoassays using magnetic particle separation
- Calculated tests like anion gap
Correct answer: Spectrophotometric assays
Lipemia, the presence of excess lipids or fats in the blood, causes turbidity which scatters light. This light scattering directly interferes with spectrophotometric methods that rely on measuring the amount of light absorbed by a solution at a specific wavelength.
Question 2: A physician orders a trough level for vancomycin, a therapeutic drug. When is the appropriate time to collect the blood specimen for this test?
- 60 minutes after the intravenous dose is complete
- Immediately after the intravenous dose is complete
- Up to 30 minutes before the next scheduled dose (Correct answer)
- At a random time between doses
Correct answer: Up to 30 minutes before the next scheduled dose
A trough level represents the lowest concentration of a drug in the bloodstream before the next dose is administered. To accurately measure this, the sample should be drawn immediately before (up to 30 minutes prior to) the next dose.
Question 3: A patient's laboratory results are as follows: Sodium: 140 mmol/L, Glucose: 180 mg/dL, BUN: 28 mg/dL. Using the most common formula, what is the calculated serum osmolality?
- 288 mOsm/kg
- 298 mOsm/kg (Correct answer)
- 300 mOsm/kg
- 318 mOsm/kg
Correct answer: 298 mOsm/kg
The standard formula for calculated osmolality is: (2 x Na) + (Glucose/18) + (BUN/2.8). Using the patient's values: (2 x 140) + (180/18) + (28/2.8) = 280 + 10 + 10 = 300 mOsm/kg. However, a slight variation of the formula is also widely used: 2 x Na + (Glucose/18) + (BUN/2.8) which gives 2 * 140 + 10 + 10 = 298. Given the options, 298 mOsm/kg is the most accurate calculation.
Question 4: A patient presents to the emergency department with chest pain. Which of the following cardiac markers is the earliest to rise following an acute myocardial infarction (AMI)?
- Creatine Kinase-MB (CK-MB)
- Lactate Dehydrogenase (LDH)
- Cardiac Troponin I (cTnI)
- Myoglobin (Correct answer)
Correct answer: Myoglobin
Myoglobin is a small protein found in heart and skeletal muscle. Due to its low molecular weight, it is released rapidly into the bloodstream following muscle injury and can be detected as early as 1-4 hours after an AMI, making it the earliest marker.
Question 5: A patient's liver function panel shows a significantly elevated Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST), with an AST:ALT ratio greater than 2:1. Gamma-glutamyl transferase (GGT) is also markedly elevated. This pattern is most suggestive of:
- Viral hepatitis
- Alcoholic liver disease (Correct answer)
- Cholestatic liver injury
- Non-alcoholic fatty liver disease
Correct answer: Alcoholic liver disease
An AST to ALT ratio of 2:1 or greater, especially in conjunction with a significantly elevated GGT, is a classic indicator of alcohol-induced liver injury.
Question 6: Which of the following pre-analytical errors is most likely to cause a falsely elevated potassium level?
- Icterus
- Using a gray-top tube
- Hemolysis (Correct answer)
- Delay in centrifugation
Correct answer: Hemolysis
Hemolysis is the rupture of red blood cells, which releases their intracellular components into the serum or plasma. Since potassium concentration is much higher inside red blood cells than in the plasma, hemolysis will cause a significant and false elevation of the measured potassium level.
Free Medical Laboratory Technician Clinical Chemistry Procedures Questions and Answers
A patient sample is received in the lab with a milky, turbid appearance.
This characteristic, known as lipemia, is most likely to interfere with which of the following?