Epidemiology Concepts

Epidemiological Triangle

• The epidemiological triangle consists of three components: agent, host, and environment, which helps in identifying disease causes and prevention strategies.

Disease Measurement and Analysis

• Positive Predictive Value (PPV) is the probability that individuals with a positive test result actually have the disease, dependent on test sensitivity, specificity, and disease prevalence.
• Odds ratio compares the odds of an event occurring in an exposed group to a non-exposed group, useful in case-control studies.
• Inferential statistics allow conclusions about a population based on sample data, using hypothesis testing, confidence intervals, and regression analysis.
• A p-value indicates the probability of obtaining results as extreme as those observed, assuming the null hypothesis is true; a value less than 0.05 suggests significance.

Disease Occurrence

• Attack rate is the proportion of exposed individuals who develop the disease, used during outbreaks to determine risk.
• Endemic disease is consistently present in a specific area or population, representing a stable disease state.
• Epidemic is a sudden increase in cases above normal expectations in a specific area.
• Pandemic is an epidemic that has spread across countries or continents, affecting a large number of people.
• Prevalence measures the proportion of individuals with a specific disease at a given time or over a specific period.
• Incidence refers to the number of new cases of a disease in a population during a specific period, indicating risk.

Biases in Research

• Selection bias occurs when study participants are not representative of the target population.
• Information bias arises from systematic errors in measurement or classification of variables.
• Confounding bias occurs when the effect of the primary exposure on an outcome is mixed with an extraneous factor.
• Recall bias happens when participants inaccurately remember past events or exposures, common in retrospective studies.
• Observer bias occurs when researcher expectations influence outcome assessment; blinding observers can reduce this.
• Publication bias occurs when studies with positive results are more likely to be published, skewing the literature.
• Response bias occurs when participants provide inaccurate responses due to social desirability or pressure.
• Survivor bias happens when only those who survive a condition or event are included in the sample.
• Healthy worker effect occurs when workers exhibit lower morbidity and mortality rates than the general population.
• Attrition bias arises when participants drop out, and the remaining differ significantly from those who left.
• Detection bias occurs when outcome determination differs across study groups; consistent assessment methods can help.
• Misclassification bias happens when participants are incorrectly categorized regarding exposure or outcome status.
• Ecological fallacy refers to making inferences about individuals based on group data.

Minimizing Biases

• Recall bias can be minimized using standardized questionnaires and validating reported information.
• Blinding participants and researchers to group assignments reduces observer and performance biases.
• Randomization helps distribute confounders evenly between groups, reducing selection bias.
• Matching pairs cases and controls with similar characteristics to control for confounding variables.
• Adjusting for confounders with statistical methods ensures the observed association is unbiased.
• Reporting bias can be mitigated by encouraging full and honest reporting.

Diagnostic Testing

• NPV is the probability that individuals with a negative test result do not have the disease, crucial for ruling out disease.
• Sensitivity measures a test's ability to correctly identify those with the disease, important for screening programs.
• Specificity measures a test's ability to correctly identify those without the disease, reducing false positives.
• Validity refers to how well a test measures what it's supposed to measure, indicating accuracy.