Review Question - QID 220337

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Evaluating Diagnostic Tests QID: 220337 (M2.OMB.13)

QID 220337 (Type "220337" in App Search)

A researcher is studying the effect of atorvastatin on preventing myocardial events in patients with hyperlipidemia. She designs a study where patients with the disease are randomized to a treatment arm or a placebo arm. Each arm involves daily treatment with atorvastatin followed by monitoring for cardiovascular events over the course of the next several years. The percentage of patients who developed events in each group is then plotted as shown in Figure A. Which value is closest to the hazard ratio for having a myocardial event in the treated group compared to the placebo group?

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0.25

0/0

0.5

0/0

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The hazard ratio is calculated as the rate of the event occurring in the treatment group compared to the event rate in the non-treatment group. In this case, the rate of a myocardial event is roughly half in the treatment group compared to the placebo group.

Hazard ratios are often used in clinical trials to compare the survival of patients receiving different treatments. The survival of a patient in these cases is defined as the time until they develop the event of interest. The hazard ratio is then a statistical measure that compares the likelihood of an event occurring in one group to another over time. Hazard ratios are calculated by dividing the hazard rate of the treatment group by the hazard rate in the control group. The hazard rate is defined as the probability of an event occurring in the next time interval divided by the length of that interval. If the ratio is less than 1, then the treatment reduces risk, and if it is greater than 1, then it represents an increased risk.

Bender and Beckmann review the use of incidence density ratios and hazard ratios in medical studies. They discuss how hazard ratios are commonly used to understand the effect of an intervention or a risk factor in influencing outcomes. They recommend using the incidence density ratio to approximate the hazard ratio in appropriate cases.

Figure/Illustration A is a diagram of the proportion of patients who have a myocardial event in the treatment and control arms. The rate of event occurrence is much higher in the control (red circle) compared to the treatment group.

Incorrect Answers:
Answer 1: A hazard ratio of 0.25 means that there is roughly a 1/4 chance of having the event occur in the treatment group compared to the control group. In this case, the risk of having a myocardial event appears to be about half as common in the treatment group compared to the control group.

Answer 3: A hazard ratio of 1 means that there is an equal risk of having the event occur in both groups. In this case, the risk of having a myocardial event is much lower in the treatment group compared to the control group.

Answer 4: A hazard ratio of 2 means that there is a higher risk of having the event occur in the treatment group. In this case, the risk of having a myocardial event is much lower in the treatment group compared to the control group.

Answer 5: A hazard ratio of 4 means that there is a much higher risk of having the event occur in the treatment group. In this case, the risk of having a myocardial event is lower in the treatment group compared to the control group.

Bullet Summary:
The hazard ratio is calculated as the rate of the event occurring in the treatment group compared to the event rate in the non-treatment group.