CBIC Surveillance 5 — Questions and Answers
Question 1: Which of the following best describes 'incidence density' as used in HAI surveillance?
- Number of new cases divided by population at risk at a single time point
- Number of new cases divided by the total time at risk (e.g., device-days) (Correct answer)
- Total cases divided by total admissions
- Cumulative cases over one year
Correct answer: Number of new cases divided by the total time at risk (e.g., device-days)
Incidence density (rate) divides new cases by the total person-time at risk, such as device-days, to account for varying exposure durations.
Question 2: Feedback of surveillance data to clinical staff is important primarily because:
- It satisfies NHSN reporting requirements
- It motivates behavior change and improvement in infection prevention practices (Correct answer)
- It eliminates the need for root cause analysis
- It reduces the time required for surveillance
Correct answer: It motivates behavior change and improvement in infection prevention practices
Sharing surveillance results with frontline staff creates awareness of performance and motivates adoption of prevention practices.
Question 3: A case definition for HAI surveillance should be established BEFORE data collection begins primarily to:
- Reduce the workload of the infection preventionist
- Ensure consistent and unbiased case identification (Correct answer)
- Limit the number of cases that must be reported
- Satisfy accreditation requirements
Correct answer: Ensure consistent and unbiased case identification
Pre-established case definitions ensure that all reviewers apply the same criteria, reducing surveillance bias and improving data comparability.
Question 4: When evaluating surveillance system usefulness, which attribute measures how quickly the system detects a health event after it occurs?
- Representativeness
- Timeliness (Correct answer)
- Flexibility
- Stability
Correct answer: Timeliness
Timeliness measures the speed between infection onset (or reporting trigger) and detection, which is critical for rapid outbreak response.
Question 5: Which type of analysis is most appropriate to determine whether an observed CLABSI cluster exceeds the expected endemic rate?
- Linear regression
- Chi-square test only
- Statistical process control (SPC) using a control chart (Correct answer)
- Point prevalence survey
Correct answer: Statistical process control (SPC) using a control chart
Statistical process control charts plot rates over time and use control limits to distinguish special-cause variation (outbreaks) from common-cause variation.
Question 6: Under NHSN reporting, which of the following infections is excluded from the CLABSI definition even if a central line is present?
- Any infection occurring more than 48 hours after admission
- Infection that meets criteria for another NHSN infection type at the same site (Correct answer)
- Coagulase-negative staphylococcal bacteremia in ICU patients
- Bacteremia in patients with a PICC line
Correct answer: Infection that meets criteria for another NHSN infection type at the same site
If a bloodstream infection meets criteria for another NHSN site-specific infection (e.g., SSI, pneumonia-related BSI), it is attributed to that site, not classified as CLABSI.
Question 7: An IP wishes to determine whether a new environmental cleaning protocol reduced C. difficile infection rates. The most rigorous study design available in a single hospital would be:
- Cross-sectional survey
- Ecological time-series analysis (interrupted time series) (Correct answer)
- Case report
- Convenience sample comparison
Correct answer: Ecological time-series analysis (interrupted time series)
An interrupted time-series analysis compares the trend in CDI rates before and after the intervention, controlling for secular trends.
CBIC Surveillance 5
Which of the following best describes 'incidence density' as used in HAI surveillance?