CIC Surveillance & Epidemiologic Investigation 2 — Questions and Answers
Question 1: Which measure best describes the probability that a surveillance test correctly identifies individuals who truly have an infection?
- Specificity
- Sensitivity (Correct answer)
- Positive predictive value
- Negative predictive value
Correct answer: Sensitivity
Sensitivity is the proportion of true positives correctly identified by a test, reflecting its ability to detect actual cases.
Question 2: An infection preventionist identifies a cluster of surgical site infections on a single unit over two weeks. What is the FIRST step in the outbreak investigation?
- Implement contact precautions for all patients
- Verify the diagnosis and confirm the cluster exists (Correct answer)
- Notify the state health department immediately
- Culture all healthcare workers on the unit
Correct answer: Verify the diagnosis and confirm the cluster exists
The first step in any outbreak investigation is to verify the diagnosis and confirm that a true cluster exists before taking further action.
Question 3: Which type of epidemiologic study design compares the frequency of an exposure between individuals with a disease and those without it?
- Cohort study
- Cross-sectional study
- Case-control study (Correct answer)
- Randomized controlled trial
Correct answer: Case-control study
Case-control studies compare exposures in cases (those with disease) versus controls (those without disease) to identify risk factors.
Question 4: A hospital reports 12 CLABSI events from 5,000 central line days. What is the CLABSI rate per 1,000 central line days?
- 0.24
- 2.4 (Correct answer)
- 24
- 0.024
Correct answer: 2.4
CLABSI rate = (12 / 5,000) × 1,000 = 2.4 infections per 1,000 central line days.
Question 5: Which NHSN surveillance definition component specifies the timeframe within which an infection must develop to be attributed to a healthcare setting?
- Risk factor window
- Date of event
- Infection window period (Correct answer)
- Secondary BSI attribution period
Correct answer: Infection window period
The infection window period (IWP) in NHSN definitions specifies the ±7-day window used to group elements of an infection into a single HAI event.
Question 6: An IP notices CAUTI rates are consistently higher on the night shift. Which type of bias is most likely affecting this finding if night-shift nurses document urinary symptoms less completely?
- Selection bias
- Confounding
- Information bias (Correct answer)
- Ecological fallacy
Correct answer: Information bias
Information bias (ascertainment bias) occurs when data collection differs systematically between groups, leading to inaccurate rate comparisons.
Question 7: In a foodborne illness outbreak investigation, the vehicle of transmission is best identified using which epidemiologic tool?
- Epidemic curve
- Attack rate table (Correct answer)
- Control chart
- Funnel plot
Correct answer: Attack rate table
An attack rate table compares illness rates among those who ate each food item versus those who did not, identifying the likely vehicle.
CIC Surveillance & Epidemiologic Investigation 2
Which measure best describes the probability that a surveillance test correctly identifies individuals who truly have an infection?