Point prevalence is best described as:

• A. Lifetime incidence
• B. Incidence rate per person-time
• C. Number ill at a point in time divided by total in group at that time
• D. Number ill in a period divided by average population

Answer: (C)

Point prevalence is a snapshot of disease burden at a single moment. It tells you what fraction of the population is ill right then, so you divide the number of people who are ill at that specific time by the total number in the group at that time. It’s a proportion, not a rate, because it doesn’t account for how long people have been ill or when new cases arise.

Lifetime incidence would be all new cases over a person’s life, a cumulative measure across time. Incidence rate per person-time is a rate of new cases per unit of person-time at risk and requires follow-up data. Period prevalence uses all cases during a defined interval divided by the average population over that interval, which blends across time rather than focusing on a single moment.

Thus, the description that matches point prevalence is the number ill at a point in time divided by the total in the group at that time.