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 prevalence in the study p as a percentage. Round to one decimal place.
Practice exercise (made-up values, not clinical guidance). A town has 33 000 inhabitants. At the start of a year, 1163 of them have a chronic disease. During the year, 201 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 test has a sensitivity of 72% and a specificity of 92%. Find the negative likelihood ratio LR−. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). A case-control study compares 300 patients with a disease (cases) and 390 people without it (controls). The table shows how many in each group were exposed to a risk factor. Find the odds ratio OR for the exposure. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). A treatment reduces the risk of an event by 30% in relative terms (RRR = 30%). In a patient group the risk without treatment (CER) is 20% over five years. Find the number needed to treat NNT for five years to prevent one event. 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 75% and specificity 91%. The prevalence of the disease is 15%. How many people with the disease are missed by the test (false negatives, FN)?
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