Calculate the excess risk of pancreatic cancer

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Reference no: EM132702684

Epidemiology 1

Problem Set 12

This problem set covers content from the beginning of the semester. This is not a final exam and will be graded as a regular problem set. The intent is to review major concepts in preparation for writing your final paper.

Question 1:
Based on national statistics, only 7.0% of all cancer deaths are due to pancreatic cancer. However, 92.3% of people diagnosed with pancreatic cancer die within the first five years after diagnosis.

Identify the two measures of disease frequency presented above.

Question 2:
One of the reasons for the low survival rate among individuals with pancreatic cancer is that there is no effective screening for this disease. It is also very rare - the incidence rate among the general population is 17/100,000 person-years. Most cases of pancreatic cancer are diagnosed when symptoms are detected, which is typically after the disease has advanced beyond a treatable stage. In an effort to improve outcomes among pancreatic cancer patients, you have developed a screening test based on costly MRI technology. The results of your test compared to the current method (symptomatic detection) are below.

MRI screening test	Symptomatic detection
MRI screening test	Yes - Pancreatic Cancer	No - No Cancer	Total
Yes - Pancreatic Cancer	14	24	38
No - No Cancer	4	99,958	99,962
Total	18	99,982	100,000

If symptomatic detection is considered the gold standard method (i.e., the truth), calculate the sensitivity, specificity, and positive predictive value (PPV) of your new test. Based on these results, explain in 2-4 sentences whether you would recommend your screening test and why.

Question 3:
Pancreatic cancer has few known risk factors; however, cirrhosis of the liver has been identified as a possible cause. In the US, cirrhosis of the liver is most commonly related to alcohol consumption. You have designed a case-control study to test the association between high alcohol consumption and pancreatic cancer. The results of your case-control study are shown below.

Exposure	Pancreatic Cancer (cases)	No Pancreatic Cancer (controls)	Total
High alcohol consumption	53	915	968
Low alcohol consumption	48	1,484	1,532
Total	101	2,399	2,500

Calculate the excess risk of pancreatic cancer among the exposed compared to the unexposed. Interpret your results in 1-2 sentences.

Question 4:
Why is a case-control study a better study design for this association than a prospective cohort study? Explain in 1-2 sentences.

Question 5:
Is recall bias likely to be a concern in this study? Explain why or why not in 1-2 sentences.

Question 6:
Smoking is a risk factor for pancreatic cancer and is known to be associated with high alcohol consumption. You are worried that the effects of smoking are confounding your results for the association between high alcohol consumption and pancreatic cancer. To examine this, you have stratified your results by smokers (former and current) and non-smokers. The results smokers are shown below.

Former and current smokers

Exposure	Pancreatic Cancer (cases)	No Pancreatic Cancer (controls)	Total
High alcohol consumption	35	408	443
Low alcohol consumption	16	255	271
Total	51	663	714

Show whether smoking is a confounder, an effect modifier, or has no impact on the association between high alcohol consumption and pancreatic cancer in your study. Justify your answer using quantifiable methods and a 1-2 sentence interpretation of your results.

Question 7:
You have consulted with a biostatistician to evaluate if your observed association is statistically significant. Which measure of significance should she give you to provide the most useful information (i.e., which tells you the most information)? Explain your choice in 1-2 sentences.
a) Confidence interval
b) P value
c) Statement of statistical significance (yes or no)

Question 8:
After adjusting for the possible effect of smoking, the biostatistician provides you with an OR and 95% confidence interval for the association between high alcohol consumption and pancreatic cancer: OR = 1.42 (0.93, 1.76). With 95% confidence, can you claim that high alcohol consumption is significantly associated with pancreatic cancer in your population? Explain your answer in 1-3 sentences.

Reference no: EM132702684

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