Practice exercise (made-up values, not clinical guidance). A town has 25 500 inhabitants. At the start of a year, 686 of them have a chronic disease. During the year, 427 more people are newly diagnosed (assume nobody moves away or dies). Find the point prevalence P at the start of the year per 1000 inhabitants. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). A town has 21 500 inhabitants. At the start of a year, 449 of them have a chronic disease. During the year, 400 more people are newly diagnosed (assume nobody moves away or dies). Find the cumulative incidence CI over the year per 1000 people at risk. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). In a randomised trial, 830 patients received a new treatment and 950 received the control treatment. The table shows how many in each group had the outcome (an unwanted event such as a stroke). Find the number needed to treat NNT to prevent one event. Round up to a whole number of patients.
Practice exercise (made-up values, not clinical guidance). A test has a sensitivity of 61% and a specificity of 79%. Find the positive likelihood ratio LR+. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). Without a drug, 29% of patients have a certain side effect during a year. The drug raises this risk with a relative risk of RR = 1.84. Find the number needed to harm NNH: how many patients must take the drug for a year for one extra patient to have the side effect? Round up to a whole number of patients.
Practice exercise (made-up values, not clinical guidance). 10 000 people are screened with a test of sensitivity 81% and specificity 93%. The prevalence of the disease is 30%. How many true-positive results TP are expected?
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