CIC Surveillance & Epidemiologic Investigation 3 — Questions and Answers
Question 1: A point-source outbreak epidemic curve typically displays which shape?
- Gradual rise over weeks with a prolonged tail
- Multiple peaks separated by the incubation period
- A sharp rise and fall within one incubation period (Correct answer)
- A plateau lasting several months
Correct answer: A sharp rise and fall within one incubation period
Point-source outbreaks show a sharp rise and fall within one incubation period because all cases are exposed simultaneously.
Question 2: Which statistical process control chart is MOST appropriate for monitoring monthly CLABSI rates over time?
- Histogram
- Pareto chart
- U-chart (or C-chart) (Correct answer)
- Scatter plot
Correct answer: U-chart (or C-chart)
A U-chart (rate-based control chart) is used to monitor infection rates per device-day over time and detect special-cause variation.
Question 3: What does the standardized infection ratio (SIR) value of less than 1.0 indicate in NHSN benchmarking?
- The observed infections exceed expected infections
- The observed infections equal expected infections
- Fewer infections were observed than expected (Correct answer)
- Data was insufficient for calculation
Correct answer: Fewer infections were observed than expected
A SIR < 1.0 means the facility had fewer infections than predicted by the NHSN baseline, indicating better-than-expected performance.
Question 4: During a Legionella outbreak investigation in a hospital, which environmental source should be prioritized for sampling?
- HVAC air filters
- Potable water system and cooling towers (Correct answer)
- Ice machines on patient floors
- Carpet and floor surfaces in patient rooms
Correct answer: Potable water system and cooling towers
Legionella thrives in water systems; potable water and cooling towers are the primary environmental sources to sample in a healthcare outbreak.
Question 5: Which denominator is used to calculate the ventilator-associated event (VAE) rate?
- Patient-days
- Ventilator days (Correct answer)
- Admissions
- Bed-days
Correct answer: Ventilator days
VAE rates are expressed per 1,000 ventilator days to account for the duration of device exposure.
Question 6: A retrospective cohort study following surgical patients finds an odds ratio (OR) of 3.5 for SSI among diabetic patients. How should this be interpreted?
- Diabetic patients are 3.5 times less likely to develop SSI
- Diabetic patients have a 3.5% absolute risk increase
- Diabetic patients are 3.5 times more likely to develop SSI (Correct answer)
- SSI risk is the same in both groups
Correct answer: Diabetic patients are 3.5 times more likely to develop SSI
An OR of 3.5 means diabetic patients have 3.5 times greater odds of developing SSI compared to non-diabetic patients.
Question 7: Which surveillance strategy focuses only on patients who meet a high-risk criterion (e.g., device use or procedure) rather than monitoring all patients?
- Prospective surveillance
- Targeted surveillance (Correct answer)
- Passive surveillance
- Laboratory-based surveillance
Correct answer: Targeted surveillance
Targeted surveillance concentrates resources on high-risk populations or procedures, improving efficiency compared to universal monitoring.
CIC Surveillance & Epidemiologic Investigation 3
A point-source outbreak epidemic curve typically displays which shape?