BOF: 2.63
A regional audit showed that
62 women who with deep vein thrombosis whilst in hospital a total of 45 women
had used oral contraception for varying periods during their lifetime. The
odds ratio can be best expressed as which of the following?
a) 45/62
b) 17/62
c) 62/17
d) 45/17
e) 62/45
Answer:
c)
The odds ratio is an estimate of relative risk and is
significant (in the absence of experimental error) at values above 1. In this
case the information available is that of oral contraceptive positive and
negative DVTs (ie cells A and C of an ABCD 2x2 table). Since we do not know
the number of women who did not have a DVT we cannot determine cells B and D
of a 2x2 table. Odds ratio is usually calculated as AD/BC. However since we do
not know the values of B and D, the best answer is A/C.
Author:
Dr. Sumantra Ray R.Nutr.
MBBS (Hons), DNHE, MICR
(UK), MRIPH (UK)
Clinical Research & Teaching Fellow
The Institute of Cardiovascular Research
University of Dundee Division of Medicine & Therapeutics
/ NHS Tayside
Honorary Invited Lecturer
Clinical Research Centre & Centre for Public Health
Nutrition Research
University of Dundee College of Medicine, Dentistry &
Nursing / NHS Tayside
Ninewells Hospital & Medical School
Dundee DD1 9SY
