Surveillance and Epidemiologic Investigation (1)

The infection preventionist (IP) is concerned about an increase in Escherichia coli infections in patients who underwent colon surgeries in the past year. What kind of graph should the IP use to determine whether the problem is ongoing?

• Scatter plot

• Line chart

• Histogram

• Mekko chart

Answer explanation

Rationale: An epidemic curve (or epi curve) is a histogram (bar chart) that shows the distribution of cases over time. The time intervals are displayed on the x-axis (the horizontal axis), and case counts are displayed on the y-axis (the vertical axis). The result is a visual representation of illness onset in cases associated with an outbreak. The epi curve is an essential tool in an outbreak investigation and a key feature of descriptive epidemiology. It can provide useful information on the size, pattern of spread, time trend, and exposure period of the outbreak, and is often included in the epidemiological (epi) summary. The epi curve should be continuously updated as the outbreak progresses..

In an assessment of 100 patients at an acute care facility, 15 patients were identified as having Candida auris, while 85 patients tested negative. What is the prevalence rate of Candida auris in this population?

• 20%

• 15%

• 10%

• 5%

Answer explanation

Rationale: The prevalence rate is calculated by dividing the number of individuals with the disease by the total population and multiplying by 100. In this case, (15/100) × 100 = 15%

A patient presents to the emergency department with a history of unprotected contact with a bat three weeks ago. The patient stated they felt like they had the flu a week ago with fever and headache, but now presents with confusion, agitation, hallucinations, insomnia, and unusual behavior such as hydrophobia. The infection preventionist reviews the physician’s orders to ensure what disease is being ruled out?

• Plague

• Leprosy

• Hantavirus

• Rabies

Answer explanation

Rationale: The first symptoms of rabies may be similar to the flu, including weakness or discomfort, fever, or headache. There also may be discomfort, prickling, or an itching sensation at the site of the bite. These symptoms may last for days.

Symptoms then progress to cerebral dysfunction, anxiety, confusion, and agitation. As the disease progresses, the person may experience delirium, abnormal behavior, hallucinations, hydrophobia (fear of water), and insomnia. The acute period of disease typically ends after 2 to 10 days. Once clinical signs of rabies appear, the disease is nearly always fatal, and treatment is typically supportive.

What is the attack rate when 20 individuals developed gastroenteritis within 24 hours of eating at a luncheon attended by 75 out of 100 invited people?

• 26.6

• 20

• 2.6

• 0.25

Answer explanation

Rationale: The attack rate is a measure used in epidemiology to determine the proportion of people who develop a specific illness among an at-risk population. In this scenario, the attack rate is calculated by dividing the number of individuals who developed gastroenteritis (20) by the total number of people who attended the luncheon (75), and multiplying the result by 100. The formula for attack rate is (Number of cases / Total population) × 100. The attack rate helps in understanding the proportion of the at-risk population (in this case, luncheon attendees) affected by the illness. This information is particularly useful in investigating outbreaks and assessing the risk of transmission.

Which of the following approaches would be most appropriate to employ to ensure the sustained reduction of central line–associated bloodstream infections following the implementation of best practices?

• Human factor analysis

• Root cause analysis

• Reliability science

• Failure mode and effects analysis

Answer explanation

Rationale: Failure mode and effects analysis (FMEA) is a systematic method for identifying potential failure modes in a system, determining their effects, and prioritizing actions to mitigate or eliminate these failures. In the context of reducing central-line associated bloodstream infections, FMEA can help the hospital’s team thoroughly analyze the potential failure modes in the process of central line insertion, maintenance, and care. By identifying these failure modes and their potential effects on infection rates, the team can prioritize interventions and strategies to prevent them from occurring, thus facilitating the sustained reduction of infections over time.

Which of the following is an example of process surveillance?

• Monitoring the number of indwelling urinary catheters per patient day

• Monitoring occurrences of surgical site infections

• Monitoring adherence to a central line insertion bundle

• Monitoring for ventilator-associated events (VAEs)

Answer explanation

Rationale: Process surveillance is the review of practices by healthcare personnel to identify whether infection prevention and control policies and procedures or best practices are being followed. The other options are examples of outcome surveillance.

A unit had 120 catheter days, 216 bed days of care, and 2 catheter associated urinary tract infections (CAUTIs) for the previous month. What is the CAUTI rate?

• 55.56 per 100 catheter days

• 9.26 per 1,000 catheter days

• 1.8 per 1,000 catheter days

• 16.67 per 1,000 catheter days

Answer explanation

Rationale: The catheter-associated urinary tract infection (CAUTI) rate is a ratio. In this scenario, the numerator is 2 (number of CAUTIs) and the denominator is 120 (number of catheter days): 2/120 = 0.01667. This number (0.01667) must then be multiplied by a constant (1,000), which results in 16.67 CAUTIs per 1,000 catheter days.

An infection preventionist is concerned about a recent increase in central line–associated bloodstream infections (CLABSIs) in the ICU. Which of the following would be the best type of surveillance to analyze gaps in practice related to this trend?

• Process surveillance of central line insertion and maintenance

• Prospective surveillance of patients with central lines for signs of bloodstream infections

• Comparative analysis of CLABSI rates between different ICUs within the hospital

• Retrospective review of medical records to identify cases of CLABSIs

Answer explanation

Rationale: Outcome surveillance involves tracking, analyzing, and reporting results such as healthcare-associated infection rates. Although outcome surveillance is essential to identify trends, the process surveillance of central line insertion and maintenance allows for the identification of practice gaps and implementation of improvement measures.

The infection preventionist needs to plan surveillance activities for the year. Which of the following is the best source of information on which to base the surveillance plan?

• An analysis of incident reports

• The annual infection control risk assessment

• The organization’s strategic plan

• Infection prevention program staffing

Answer explanation

Rationale: Surveillance activities should be prioritized based on the annual infection control risk assessment. Although the other choices may affect the infection prevention program, they do not help identify needed surveillance activities.

The infection preventionist works in an acute care medical center with 250 beds. The total bed days of care during the previous 12 months was 25,000, and the ventilator days of care were 2,000. There were 20 ventilator-associated events (VAEs). What was the VAE rate for the past 12 months?

• 0.8 per 1,000 ventilator days

• 0.08 per 100 ventilator days

• 10 per 1,000 ventilator days

• 0.74 per 1,000 ventilator days

Answer explanation

Rationale: The ventilator-associate event (VAE) rate is calculated by dividing the number of VAEs (20) by the number of ventilator days of care (2,000) and multiplying by a constant (1,000).