Question

A clinical trial is run to look at the efficacy of a new blood pressure drug. Patients with a diagnosis of hypertension (high blood pressure) are recruited to participate in the trial and randomized to receive either the new drug or placebo. Participants take the assigned drug for 12 weeks and their blood pressure status is recorded. At the end of the trial, participants are classified as still having hypertension or not. The data are shown here:

Group	Number with Hypertension at 12 weeks	Number Free of Hypertension at 12 Weeks
Placebo	44	6
New Drug	36	14

1.What was the prevalence of hypertension at the start of the trial?

2.What was the prevalence of hypertension at the end of the trial?

3.What was the incidence of recovery over the course of the trial?

4.Compute the relative risk of hypertension, comparing the new drug and the placebo.

5.Based on the results above, what can you conclude about the efficacy of the new drug?

Answer 1

Answer:

Based on the given data:

Contigency 2 X 2 table
Group	Number with Hypertension at 12 weeks (Disease)	Number Free of Hypertension at 12 weeks (No Disease)	Total
New Drug (Exposed)	36 (a)	14 (b)	50 (a + b)
Placebo (Unexposed)	44 (c)	6 (d)	50 (c + d)
Total	80 (a + c)	20 (b+d)	100 (a+b+c+d)

This is a 2x2 contingency table.

What was the prevalence of hypertension at the start of the trial?

• At the start of the trial, prevalence of Hypertesion was 100% as the subjects suffering from Hypertension were selected to be a part of this study.

2.What was the prevalence of hypertension at the end of the trial?

• Prevalence = Total patients with Hypertension / Total number of patients = 80/100 = 0.800 or 80%

3.What was the incidence of recovery over the course of the trial?

• Incidence of recovery with drug = 14/50 = 0.28 or 28%
• Incidence of recovery with placebo = 6/50 = 0.12 or 12%

4.Compute the relative risk of hypertension, comparing the new drug and the placebo.

• Relative risk = [a/(a+b)] / [c/(c+d)] = =(36/(50) / (44/(50) = 0.8182 = 81.8%

5.Based on the results above, what can you conclude about the efficacy of the new drug?

• Based on the results above, drug seems to be effective in decreasing the risk of hypertension.
• A relative risk of 0.82 means 18% reduction in the relative risk of the specified outcome in the treatment group compared with the control group.