CBIC Epidemiology 5

Question 1

Which of the following best describes the 'iceberg phenomenon' in infectious disease epidemiology?

Accepted Answer

Most infections in a community are subclinical and go undetected

Answer

The iceberg phenomenon describes how clinical cases represent only the visible 'tip' of all infections, while the majority — subclinical and mild cases — remain undetected below the surface.

Question 2

When comparing HAI rates between two ICUs with different patient populations, which statistical method best adjusts for differences in intrinsic patient risk?

Accepted Answer

Standardized infection ratio with risk adjustment

Answer

Risk-adjusted standardized infection ratios use multivariate models or stratification to account for patient-level risk factors, enabling fair comparisons across facilities with different case mixes.

Question 3

In an investigation of a suspected nosocomial Clostridium difficile outbreak, which case definition component is essential for the initial case count?

Accepted Answer

Symptom criteria combined with laboratory confirmation and healthcare exposure criteria

Answer

A sound case definition combines clinical criteria (diarrhea), laboratory confirmation (positive toxin or PCR), and an epidemiological link (healthcare exposure) to ensure cases are counted consistently and accurately.

Question 4

Which epidemiological concept explains why routine screening programs for low-prevalence infections often yield many false-positive results even with high-specificity tests?

Accepted Answer

Positive predictive value decline with low prevalence

Answer

When disease prevalence is low, even highly specific tests produce many false positives relative to true positives, dramatically reducing the positive predictive value (PPV) of the test.

Question 5

A prospective study follows 500 uninfected patients for 6 months; 50 develop SSI. What is the cumulative incidence of SSI?

Accepted Answer

10%

Answer

Cumulative incidence = new cases / total at-risk population at the start = 50 / 500 = 0.10, or 10%, over the 6-month follow-up period.

CBIC - Certification Board of Infection Control Practice Test

CBIC - Certification Board of Infection Control Practice Test

CBIC Epidemiology 5