1 Case-control study of of BCG vaccination and leprosy. 2 Case ...

Case-control study of renal cancer and trichorehtene 1
1 Case-control study of of BCG vaccination and leprosy.
New cases of leprosy were examined for presence or absence of the BCG scar. During the same
period, a 100% survey of the population of this area, which included examination for BCG scar,
had been carried out.
The tabulated data refer only to subjects under 35, because vaccination was not widely available
when older persons were children.
A random smaple of 1000 controls was sampled, and their status is given in the last column:
BCG scar Leprosy cases Population survey Sampled controls
Present 101 46 028 554
Absent 159 34 594 446
1. Calculate the odd-ratio of leprosy between persons with and persons without BCG-scar.
2. Open bcg-1.sas in the program editor and do the analysis using the total population as
controls.
3. Change the number of controls in the datalines command (highlighted in yellow) so they
refer to the sampled dataset.
How does the odds-ratio, and the log-odds-ratio and its standard error change
2 Case-control study of of BCG vaccination and leprosy. (2)
1. Open bcg-2.sas in the program editor and do an age-stratified analysis using the total
population as controls, table 18.1, p. 175. Make sure you find the results from Clayton &
Hills in exc. 18.3, p. 178.
2. Change the number of controls in the datalines command (highlighted in yellow) so they
refer to simulated dataset ( table 18.2, p. 179), and do the stratified analysis.
How does the estimate of the OR and the confidence interval change
3. Change the number of controls in the datalines command (highlighted in yellow) so they
refer to matched dataset ( table 18.3, p. 179), and do the stratified analysis.
How does the estimate of the OR and the confidence interval change
3 Case-control study of renal cancer and trichorehtene
Vamvakas et al.: Renal cell cancer correlated with occupational exposure to trichlorethe. J Cancer
Res Clin Oncol, 1998, pp 374–382.
The paper is available at the course homepage as http://www.pubhealth.ku.dk/~bxc/Epi.
2007/Vamvakas.1998.pdf
We will discuss the following points based on the papaer:
1. What is the primary aim of the study
2. How were the cases sampled

2 Epidemiology, autumn 2011
3. How were the controls sampled
4. Are they comparable; i.e. what assumptions are needed
5. What is the (actual) study base
6. What study base is the intended (for generalization)
7. Is the sampling scheme incidence density sampling
8. Can the age-effect on the occurrence of renal cancer be estimated
9. Is age a confounder
10. What is the main result (in plain words)
11. Key in the numbers in table 6 (p.380), and verify the analysis using SAS proc freq. In
particular, how does the odds-ratio estimate given by Vamvakas et al. compare the the
Mantael-Haenszel estimate based on the same data