Ask the treatment expert: calculating pressure ulcer prevalence vs. incidence
Ask the treatment expert
Prevalence studies measure the number of a defined set of patients who have a pressure ulcer at a particular moment in time. Prevalence includes those admitted to the facility with a PU and those who have developed one between admission and the time of the study.
They give a one-time only “snapshot” of the number of cases at a given time, specific date, specific time, specific population, and indicate burden of PUs.
Incidence studies identify the rate of occurrence of new pressure ulcers over a specific time period.
Incidence studies help to identify facility-acquired pressure ulcers, give the rate of new cases that are developed, multiple observations, specific population, and will provide the clearest indication of the effectiveness of a PU prevention protocol.
Because prevalence and incidence are expressed in terms of patients, it is important that studies of PU occurrence count patients with PUs, not individual PUs themselves.
To determine the rate of pressure ulcer prevalence:
1. Divide the total number of patients with pressure ulcers by the total number of patients (census) = A
2. Multiply A x 100 = prevalence rate
3. Example: 20 patients with PU / Census of 176 = 0.11 x 100 = 11%
To determine the rate of pressure ulcer incidence:
1. Divide the total number of patients developing a PU during the specified time period by the total number of patients (census) = A
2. Multiply A x 100 = incidence rate
3. Example: 5 patients with new PU/Census of 176 = 0.028 x 100 = 2.8%
New international guidelines can be downloaded at http://tinyurl.com/PUstudies.