In a study on the relationship between oral contraceptives (OCs) and urinary tra
ID: 70203 • Letter: I
Question
In a study on the relationship between oral contraceptives (OCs) and urinary tract infections, 500 women who use OC and 3000 women who do not use OCs were monitored over a period of three years.
Table: New cases of urinary tract infections
1. What is the prevalence of urinary tract infections in the first year?
2. What is the odds ratio as it relates to urinary tract infections?
3. How many cases of urinary tract infections associated with the use of OCs are expected per year in a population of 10 000 people of which 55% are women of which 20% use OCs?
Year Uses OCs Do not use OCs 1 15 35 2 30 70 3 20 33Explanation / Answer
Ans 1. For first year
Total no. of women who use OCs = 500
No. of women with new case of UTI who uses OCs= 15
Therefore prevalence of UTI in the women who uses OCs= 15/500*100
= 3%
Total no. of women who do not use OCs = 3000
And the no. of women who are suffering with UTI = 35
Therefore prevalence of UTI in women who do not use OCs = 35/3000*100
=1.1%
Ans2. The odd figure is that in the third year there are less new cases of UTI in both the women using OCs and those who don’t use OCs.
Ans3. According to the given table in first year women using OCs have 3% new cases of UTI
Similarly for second year,
Prevalance =30/500*100 =6%
For third year,
Prevalance = 20/500*100
=4%
Therefore average prevalence per year =( 3+6+4)/3
=13/3 = 4.3%
So, For given problem,
Total population = 10000
No. of women =55% of 10000 =5500
No. of women using OCs = 20%5500
=1100
Therefore the expected UTI case per year in women using OCs =4.3% of 1100
= 47.3 = 47 women.
Therefore per year 47 women suffering from UTI.
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