The genetic patterns of disease are the basis for understanding why people are susceptible to particular diseases. They also provide a framework for understanding how the immune system may be affected by the development of certain diseases.
The genetic pattern of a disease is defined as the combination of alleles (gene variants) that predispose an individual to develop that particular disease. This can be determined by studying family members who have had the disease, or by comparing blood samples from people with and without the disease.
Genetic patterns of the disease may be categorized in several ways:
- Frequency – The frequency of a rare allele in a population can help determine whether a person is at increased risk of developing that condition. For example, having one copy of the “extremely high blood pressure” allele (hypertensive disorder) increases your chances of developing hypertension by more than 50 times compared to someone who does not have this allele. In contrast, having two copies does not increase your chances at all – even though you will still be at risk for developing hypertension if you do not take action to prevent it.
- Odds Ratio – This is an estimate of how likely it is that an individual will develop a certain condition because he or she has a particular genotype compared to those without it. Odds ratios are most often used when the outcome of interest is rare, and the frequency of the risk allele is unknown.
- Relative Risk – This is an estimate of how likely it is that an individual will develop a certain condition because he or she has a particular genotype compared to those without it. Relative risk is most often used when the outcome of interest is common.
- Prevalence – This is the proportion of a population that has a particular condition at any given time.
- Incidence – This is the rate at which new cases of a disease are diagnosed.
- Morbidity – This is the percentage of people who have a certain condition but do not know about it or do not seek treatment for it.
- Mortality – This is the proportion of people who die within a specified time period due to their disease.
- Case fatality rate – This is the proportion of people with a certain disease who die within a specified time period.
- Recovery rate – This is the percentage of people who recover from a certain condition.
- Disability-adjusted life years (DALYs) – This is a measure used by epidemiologists to quantify both the quality and quantity of life lost due to premature mortality and morbidity due to disease, trauma, or other health conditions.