Medical Technologist Test Medical Technologist General Information 4 — Questions and Answers
Question 1: A systematic error in laboratory testing is best characterized by:
- Random scatter of results around the mean
- Consistent bias in one direction affecting accuracy (Correct answer)
- Single outlier values that are unpredictable
- Increased imprecision with no directional trend
Correct answer: Consistent bias in one direction affecting accuracy
Systematic errors cause a consistent directional shift (positive or negative bias) in results, affecting accuracy without necessarily changing precision.
Question 2: Which specimen type is preferred for measuring ionized calcium?
- Serum collected in SST tube
- Plasma collected in heparin tube analyzed immediately (Correct answer)
- Whole blood collected in EDTA tube
- 24-hour urine collected with HCl preservative
Correct answer: Plasma collected in heparin tube analyzed immediately
Heparinized plasma is preferred for ionized calcium because EDTA and citrate chelate calcium, and the specimen must be analyzed immediately to prevent pH shifts.
Question 3: Delta checks in the laboratory are used to:
- Compare a patient's current result with their previous result to detect errors (Correct answer)
- Verify reagent lot-to-lot consistency
- Identify instrument carry-over between samples
- Monitor QC performance over extended time periods
Correct answer: Compare a patient's current result with their previous result to detect errors
Delta checks compare a patient's current result to their previous result; a large unexpected change flags potential specimen identification errors or acute clinical events.
Question 4: The reference interval (reference range) for a laboratory test is typically established using results from:
- Hospitalized patients with similar diagnoses
- 95% of results from a healthy reference population (Correct answer)
- The middle 50% of all patients tested in the past year
- International consensus guidelines regardless of local population
Correct answer: 95% of results from a healthy reference population
Reference intervals are defined as the central 95th percentile of results from a carefully selected healthy reference population, meaning 2.5% fall above and below.
Question 5: Which type of pipette is most precise for delivering an exact volume in laboratory procedures?
- Mohr pipette
- Volumetric (transfer) pipette (Correct answer)
- Serological pipette
- Pasteur pipette
Correct answer: Volumetric (transfer) pipette
Volumetric (transfer) pipettes are calibrated to deliver a single exact volume with the highest accuracy, indicated by a single graduation mark.
Question 6: An autoclave sterilizes materials using:
- Dry heat at 320°F for 2 hours
- Saturated steam under pressure at 121°C for 15-30 minutes (Correct answer)
- UV radiation for 30 minutes exposure
- Ethylene oxide gas at room temperature
Correct answer: Saturated steam under pressure at 121°C for 15-30 minutes
Autoclaves use saturated steam at 121°C (250°F) under 15 psi pressure for 15-30 minutes to achieve sterilization by denaturing microbial proteins.
Question 7: The coefficient of variation (CV%) is used in laboratory medicine to express:
- The absolute difference between duplicate measurements
- Imprecision as a percentage relative to the mean (Correct answer)
- The ratio of systematic to random error
- Accuracy deviation from a reference method
Correct answer: Imprecision as a percentage relative to the mean
CV% = (SD/mean) × 100, expressing the standard deviation as a percentage of the mean to allow comparison of imprecision across different analytes or concentrations.
Medical Technologist Test Medical Technologist General Information 4
A systematic error in laboratory testing is best characterized by: