Excerpt from: McKnight's (click for full article)
Prevalence is defined as a cross-sectional count of the number of cases at a specific point in time, or the number of people with pressures ulcers who exist in a patient population at a given point in time.
Prevalence indicates the number of pressure ulcers whether they are present upon or developed after admission. It is a snapshot of the number cases at any given time.
Incidence is defined as the number of new cases appearing in a population and indicates the rate at which new disease occurs in population previously without disease. Incidence will capture the percentage of patients that have developed a new pressure ulcer while in your facility.
To calculate the prevalence rate:
Take the number of residents with any pressure ulcer and divide by the total number of residents during that month.
Multiply the results by 100. This equals the prevalence rate.
Example of prevalence rate: 8 residents with pressure ulcers divided by 100 census = 0.08.
Multiply 0.08 by 100 and you get 8%.
To calculate the incidence rate:
The number of residents with a new pressure ulcer developed after admission divided by the total number of residents admitted during that time.
Multiply the results by 100. This equals the incidence rate.
Example of incidence rate: 2 residents with a new pressure ulcer divided by 100 census = 0.02.
Multiply 0.02 by 100 and you get 2%.
With both, count only the number of residents, not the number of ulcers.