JNTU Pharm. D V Year PHARMACOEPIDEMIOLOGY AND PHARMACOECONOMICS Previous Question Paper (October/November - 2019 - R08)

Risk measurement is the cornerstone of pharmacoepidemiology, allowing researchers to quantify the association between drug exposure and health outcomes. These measurements are primarily derived from the comparison of incidence rates or proportions between exposed and unexposed groups.

The fundamental measures of risk include:

1. Cumulative Incidence (Risk): The probability that an individual will develop a disease over a specified period. It is calculated as the number of new cases during a period divided by the number of disease-free subjects at the start of the period.
2. Incidence Density (Rate): The frequency of new events per unit of person-time. It is calculated as the number of new cases divided by the total person-time at risk, providing a more accurate measure when individuals are followed for different durations.
3. Relative Risk (RR): The ratio of the risk in the exposed group to the risk in the unexposed group. It indicates the strength of the association between drug use and the outcome. A value of 1 implies no association, while values greater than 1 suggest an increased risk.
4. Odds Ratio (OR): Commonly used in case-control studies, it represents the ratio of the odds of exposure among cases to the odds of exposure among controls. It serves as an estimate of the relative risk when the disease is rare.
5. Attributable Risk (AR): Also known as Risk Difference, it measures the absolute difference in risk between the exposed and unexposed groups. It quantifies the excess risk attributed to the drug exposure.
6. Number Needed to Harm (NNH): The inverse of the attributable risk (1/AR). It represents the number of patients who need to be exposed to a drug for one additional adverse event to occur.

These measures are essential for evaluating drug safety, identifying potential side effects, and supporting regulatory decision-making. The choice of measure depends on the study design—such as cohort or case-control—and the nature of the outcome being investigated.