HTH 450: Observational Studies in Epidemiology

Vocabulary practice flashcards covering case reports, ecologic designs, cross-sectional studies, case-control designs, case-crossover studies, and associated biases from Chapter 7 of HTH 450 Epidemiology.

Case Report

A descriptive document detailing a particular clinical phenomenon, diagnosis, and clinical management in a single patient based on routine clinical observation.

Case Series

A study that describes a group of more than one patient presenting with similar clinical problems or characteristics, often used as an early hypothesis-generating tool.

Ecologic Study

An observational study design that investigates group-level characteristics and aggregate data rather than individual-level data to explore potential associations.

Ecologic Fallacy

A logical error that occurs when conclusions about individual members of a group are inferred solely from characteristics of the group as a whole, erroneously assuming group-level truths apply to each individual.

Cross-Sectional Study

An observational study design (also known as a prevalence study) where both exposure and disease outcome are assessed simultaneously in each participant, providing a snapshot of a population at a single point in time.

Temporal Bias

A bias inherent to cross-sectional studies that arises because data are collected at a single point in time, failing to capture the dynamic nature of variables and preventing the establishment of a temporal sequence between exposure and outcome.

Survival Bias

A specialized form of selection bias in cross-sectional studies where only prevalent cases are captured, systematically excluding individuals who died rapidly after disease onset prior to study execution.

Cross-Sectional Study $2 \times 2$ Table Analysis

The dual calculation methods used in cross-sectional analyses: calculating the prevalence of disease in exposed versus nonexposed individuals ($\frac{a}{a+b}$ vs. $\frac{c}{c+d}$) or the prevalence of exposure in diseased versus nondiseased individuals ($\frac{a}{a+c}$ vs. $\frac{b}{b+d}$).

Serial Cross-Sectional Study

A study design that repeats cross-sectional surveys across multiple successive time points (such as NHANES data) to track and evaluate temporal trends in disease prevalence for policy and planning.

Case-Control Study

An observational study design that identifies individuals with a specific disease ('cases') and suitable individuals without the disease ('controls') to retrospectively determine and compare prior exposure histories.

Case-Control Study Design Flowchart

The sequential procedure in which investigators first assemble cases and controls (Step A), retrospectively measure past exposure status for both groups (Step B), and compare exposure proportions to assess whether cases have higher exposure than controls (Step C).

Hospital-Based Selection Bias

A bias occurring in case-control studies when cases or controls are drawn from a single medical center whose unique referral patterns or admission practices prevent results from generalizing to the broader diseased population.

Limitations in Recall

An information collection limitation where study participants are constrained by natural human memory constraints in accurately recounting past events, or simply lack the requested historical information.

Recall Bias

A systematic difference in the accuracy or completeness of past exposure recollection between study groups, commonly occurring when diseased cases reflect on and report prior exposures differently than controls.

Confounder

An extraneous factor or characteristic that differs between cases and controls and is related to both exposure and outcome, potentially producing an observed association that is not causal.

Matching

A methodological procedure in case-control studies where controls are chosen to have a distribution of confounding variables (such as age or socioeconomic status) identical to that of cases, eliminating confounding by those variables.

Case-Crossover Design

An observational study design used for acute outcomes triggered by transient, short-lived exposures, in which each participant serves as their own control by comparing exposure during the period immediately before the event to a more remote control time period.

At-Risk Period

The defined time window immediately preceding an acute event in a case-crossover design during which the transient exposure level is measured and compared to an uninjured baseline control period.