Question

A randomized clinical trial was designed to test the efficacy of a new serotonin-reuptake inhibitor (anxiety reducing drug – ARD) to treat the symptoms of anxiety compared to a more traditional approach of behavioral therapy. The trial randomized 1,200 men and women with untreated anxiety symptoms in a 1:1 ratio to either 1) treatment with ARD, and 2) weekly behavioral therapy sessions. The primary endpoint was resolution of anxiety based on results from a validated anxiety assessment instrument. At six months of follow-up it was found that 200 persons in the ARD group and 50 in the behavioral therapy group met the primary endpoint.

-Create a 2X2 table below and calculate the relative risk of anxiety symptoms for persons in the behavioral therapy group compared to those taking ARD. State your results in a sentence.

- Calculate the efficacy (as risk reduction) of ARD compared to behavioral therapy. State your results in a sentence.

-How many patients with untreated anxiety would you need to treated with ARD

(instead of behavioral therapy) to resolve the symptoms of anxiety over 6 months?

-In performing the analysis, it was discovered that men responded better to ARD than women, but they had similar responses to behavioral therapy. Also, the majority of subjects in the study were women. How might this affect your results? Can you suggest a study design that might improve the validity of your findings?

Answer 1

The total number of population here is 1200.

No. of people in the ARD group having anxiety = 200

No. of people in the Behavioural therapy group having anxiety = 50.

Now we will construct the 2 X 2 table : (The table below is always constructed in this way with the same row and column headings because if these headings change then the complete formula of relative risk will change)

	DISEASE ( HAVING ANXIETY)	NO DISEASE (NOT HAVING ANXIETY)	TOTAL
ARD GROUP	(a) 200	(b) 475	675
BEHAVIOURAL THERAPY	(c) 50	(d) 475	525
TOTAL	250	950

Relative Risk = = = 3.11

Since the relative risk is greater than 1 we have that the people in ARD group have more risk of having anxiety than the ones in the Behavioural therapy group.

If the risk was equal to one then both the groups would have same amount of risk, and if the risk was less than 1 then the ARD group would have less risk than the behavioural therapy group.

(b) Basically the relative risk reduction means the decrease of probability is the recognitional risk of one group of people to another. Now the formula for the relative risk reduction is 1 - relative risk = -2.11. Since the relative risk reduction is less than 1 , it signifies that the risk of developing anxiety is reduced by this percentage.

(c) From the table we can see that 475 no. of people should be treated with ARD group rather than the behavioural therapy.