Which study design was used to assess risk factors for CLABSIs in hematologic and oncologic patients?

• A. Case-control
• B. Prospective cohort
• C. Retrospective cohort
• D. Cross-sectional

Answer: (C)

A retrospective cohort design fits this scenario because it allows you to use existing medical records to define a group of hematologic or oncologic patients with central lines, identify who developed a CLABSI, and look back at exposures before the infection occurred. This approach lets you examine multiple risk factors—such as catheter type and duration, neutropenia, chemotherapy regimens, mucosal barrier injury, and line-care practices—and estimate how they relate to the risk of CLABSI, often generating incidence measures or relative risks. The temporality is preserved (exposures precede infection) even though the data are collected after the fact, making it a practical and efficient choice in this patient population.

In contrast, a case-control design starts with those who have the infection and those without, then looks back for exposures, which is efficient for rare outcomes but less direct for assessing risk within a defined population and for estimating incidence. A prospective cohort would be ideal but requires more time and resources, while a cross-sectional study captures exposure and outcome at one point in time, making it hard to establish the sequence of events needed to assess risk factors.