Practice exercise (made-up values, not clinical guidance). A town has 38 500 inhabitants. At the start of a year, 516 of them have a chronic disease. During the year, 744 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 new test was compared with the reference standard in a study (see the 2 × 2 table). Find the negative predictive value NPV as a percentage. Round to one decimal place.
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 positive likelihood ratio LR+. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). A test has a sensitivity of 62% and a specificity of 67%. Find the positive likelihood ratio LR+. Round to two decimal places.
Practice exercise (made-up values, not clinical guidance). Without a drug, 40% of patients have a certain side effect during a year. The drug raises this risk with a relative risk of RR = 2.27. 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 patient has a pre-test probability of 10% for a disease. A test with sensitivity 70% and specificity 63% comes back positive. Find the post-test probability p′ of the disease as a percentage. Round to one decimal place.
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