A study is conducted to estimate the prevalence of catheter-associated urinary tract infection (CAUTI) in the intensive care unit (ICU) of an urban hospital. The plot below shows the number of cases of CAUTI in this hospital during the month of July among patients in the ICU. Based on the plot, which of the following is the number of prevalent cases on July 31?
Show Explanatory Sources
Prevalence refers to the proportion of diseased individuals in a particular at-risk population, often measured in the following ways:
Period prevalence refers to the number of disease cases in a period (eg, from July 1 to July 31) divided by the number of people in the at-risk population (ie, prevalent cases at the beginning of a period plus any incident cases during the period).
Point prevalence refers to the number of disease cases that are active at a specific point in time (eg, July 31) divided by the number of people in the at-risk population.
In this example, a study determined the number of cases of catheter-associated urinary tract infection (CAUTI) among patients in the intensive care unit during the month of July. There were 9 cases of CAUTI in July; a tenth case developed after July 31. Four of the 9 patients recovered before July 31; therefore, the number of cases of CAUTI still active on July 31 was 5.
(Choice A) Only 1 patient had developed CAUTI before July 1; this represents the number of point-prevalent cases on July 1.
(Choice B) Four patients with CAUTI recovered during the month of July.
(Choice D) Eight cases of CAUTI developed between July 1 and July 31; this represents the number of incident cases during July.
(Choice E) There were 9 cases of CAUTI during the month of July; this represents the number of period-prevalent cases.
Educational objective:
Unlike period prevalence, point prevalence considers only the number of disease cases that are active at a specific point in time.