Practise Qs Flashcards
Which of the following research objectives cannot be achieved using observational data:
A: to measure the incidence of breast cancer in women in the UK
B: to determine the effectiveness of a new cancer drug compared to a placebo
C: to identify differences in colon cancer survival between affluent and deprived populations
D: to evaluate the effectiveness of a national Cancer control policy
B: to determine the effectiveness of a new cancer drug compared to placebo
A group of people were recruited to a study and data was collected on their smoking habits. The group was then followed for 10 years and the occurrence of lunch cancer in smokers was compared to nom-smokers.
What type of study is this an example of?
A cohort study
In 2019, 50 cases of malignant melanoma were diagnosed in Nottingham and 100 in London. This does not tell us that malignant melanoma is more frequent in London than Nottingham because:
A: the population size of the 2 cities is different
B: the population of London is more affluent
C: the population of London has a higher exposure to UV radiation
D: a different coding system is used to register cancers
E: there are regional differences in survival from malignant melanoma in England
A: the population size of the 2 cities is different
100 initially healthy people were followed up for 7 years. Over time 10 people developed cancer and 90 remained disease free. The total person-time at risk was 650 person-years.
What is the risk of developing cancer in this cohort?
What is the odds of developing cancer in this cohort?
Risk = no.new cases/population initially at risk, 10/100 = 10%
Odds = no.new cases / no.people remain disease free = 10/90 = 11%
Case control study investigating associating between dietary fibre and colon cancer:
Fibre intake high: CC yes (cases): 5, CC no (control) 117
Five intake low: CC yes 15, CCno 63
How would you calculate the odds ratio of CC in the high intake group compared to low intake?
Odds in high: 5/117 (=0.043)
Odds in low: 15/63 (=0.238)
Odds ratio = odds in exposed (high)/odds in unexposed (low) = 0.043/0.238 =0.18
What is the lifetime risk of breast cancer among women with a BRCA1/2 mutation?
50-85%
What proportion of cancer deaths worldwide will occur in developing countries?
65%
The mortality rates of stomach cancer in central American is 19.9/100,000 and in Europe 33.9/100.000. What 2 reasons suggest why stomach cancer mortality appears higher in Europe?
A: the regions have 2 different health care systems
B: the population in Europe is older than central America
C: the prevalence of h pylori infection is higher in Europe
D: the incidence of stomach cancer is higher in older people
E: survival from gastric cancer is higher in Europe than central america
B & D
Screening test positive: Cancer yes 34, cancer no 97
Screening test negative: cancer yes 19, cancer no 500
What is the sensitivity of the test?
Sensitivity = true positive / true positive + false positive
= 34 / (34+19)
= 34/45
= 64%
