Practice exercise (made-up values, not clinical guidance). A new test was compared with the reference standard in a study (see the 2 × 2 table). Find the accuracy Acc as a percentage. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). A town has 43 000 inhabitants. At the start of a year, 1083 of them have a chronic disease. During the year, 616 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, 700 patients received a new treatment and 640 received the control treatment. The table shows how many in each group had a side effect. Find the number needed to harm NNH: how many patients must be treated 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). A test has a sensitivity of 80% and a specificity of 69%. Find the positive likelihood ratio LR+. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). Without a drug, 27% of patients have a certain side effect during a year. The drug raises this risk with a relative risk of RR = 1.95. 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). A screening test has a sensitivity of 87% and a specificity of 84%. It is used in a population where the prevalence is 2%. Find the positive predictive value PPV as a percentage. Round to one decimal place.
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