Surveillance & Epidemiologic Investigation Flashcards

Which measure best describes the probability that a surveillance test correctly identifies individuals who truly have an infection?

Answer: Sensitivity

Sensitivity is the proportion of true positives correctly identified by a test, reflecting its ability to detect actual cases.

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?

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.

Which type of epidemiologic study design compares the frequency of an exposure between individuals with a disease and those without it?

Answer: Case-control study

Case-control studies compare exposures in cases (those with disease) versus controls (those without disease) to identify risk factors.

A hospital reports 12 CLABSI events from 5,000 central line days. What is the CLABSI rate per 1,000 central line days?

Answer: 2.4

CLABSI rate = (12 / 5,000) × 1,000 = 2.4 infections per 1,000 central line days.

Which NHSN surveillance definition component specifies the timeframe within which an infection must develop to be attributed to a healthcare setting?

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.

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?

Answer: Information bias

Information bias (ascertainment bias) occurs when data collection differs systematically between groups, leading to inaccurate rate comparisons.

In a foodborne illness outbreak investigation, the vehicle of transmission is best identified using which epidemiologic tool?

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.