Assignment 2: LITERATURE APPRAISAL
Instructions to students: This is a take-home assignment. Students are to work individually and submit precisely written or sketched answers. Most answers should not require more than five (5) lines of text. You do not need to supply any referencing. CLEARLY indicate which question you are answering. This assignment constitutes twenty-five percent (25%) of the total marks
Submitting assignment: No hardcopy submission is required. The latest cut-off is by 5 pm on the due date.
Article to read: German Outbreak of Escherichia coli O104:H4 Associated with Sprouts.
http://www.nejm.org/doi/full/10.1056/NEJMoa1106482
Reference: Buchholz U, Bernard H, Werber D, Böhmer MM, et al. New England Journal of Medicine 2011; 365:1763-1770.
QUESTIONS (Total: 25 marks)
1. (a) What is the advantage of using a matched case-control design compared to unmatched case-control design? (b) What variables were matched? (4 marks)
2. How was information about exposures obtained in the case-control design? (1 mark)
3. What is the main advantage of having broader definition of the outcome in the cohort study compared to the case-control study? (2 marks)
4. (a) Give the formula for estimating the total number of HUS cases caused by eating contaminated sprouts in restaurant K during the study period.
(b) if the total number of main dishes served containing contaminated sprouts was 120 and the attack rate among sprout eaters was 30%, what is the estimated number of HUS cases? (4 marks)
5. What is the meaning of (a) attack rate among sprout eaters and
(b) attack rate for subjects fulfilling case definition (see Table 2, last column) (2 marks)
6. If sprouts are the contaminated source, which attack rate would you expect to be bigger? (1 mark)
7. (a) How is the exposure-outcome association expressed for the case-control study analysis? (See Table 1)
(b) Which food item in Table 1 is the most likely contaminated source, why?
(c) Express the association between consuming that food item and the chance of
getting HUS in simple language.
(d) What is the importance of also reporting the 95% CI? (6 marks)
8. (a) How is the exposure-outcome association expressed for the cohort study
analysis? (See Table 3)
(b) Calculate the association between consuming sprouts and getting infected as a
Risk Difference.
(c) Express the meaning of this risk difference association in simple language. (5 marks)