Which study has a cross-sectional design?
A. Participants are assessed at baseline and then again every 3 months for two years for occurrence of disease
B. Patients who recovered from COVID-19 infection are matched and compared with patients who recovered from the seasonal fiu for harmful lasting effects
C. Patients are randomly selected to use one of 2 drugs for arthritis symptoms and followed over time to assess treatment response
D. A random sample of auto mechanics is tested for lead poisoning
The correct answer and explanation is:
The correct answer is D. A random sample of auto mechanics is tested for lead poisoning.
Explanation:
A cross-sectional study design involves observing or measuring a specific characteristic or outcome in a population at one single point in time. This design provides a “snapshot” of the frequency or characteristics of a disease or condition in a defined population at a particular moment. It does not follow participants over time or assess changes.
Let’s analyze each option:
- Option A describes participants being assessed at baseline and then repeatedly every 3 months for two years. This means data are collected over time, making it a longitudinal study, not cross-sectional.
- Option B compares two groups of patients with different past infections to assess harmful lasting effects. This is a comparative or case-control study where past exposures or outcomes are compared between groups, not a single-time observation.
- Option C involves random assignment of patients to two different drugs and following them over time to measure treatment response. This is a randomized controlled trial, an experimental design, which follows participants longitudinally.
- Option D involves testing a random sample of auto mechanics at a single point in time for lead poisoning. This is the classic cross-sectional approach, where data are collected once to assess the prevalence of lead poisoning in this group.
Cross-sectional studies are useful for determining the prevalence of a condition or risk factor in a population. They are relatively quick and inexpensive compared to longitudinal designs. However, because data are collected at one point in time, cross-sectional studies cannot determine causality or the sequence of events (which comes first, exposure or outcome).
In summary, option D best fits the definition of a cross-sectional study because it involves measuring a health outcome (lead poisoning) in a population (auto mechanics) at one specific time.