epidemiology

epidemiology
Assignment 2b
Assessing Relationships: Plague in a Case-Control Study & the
Odds Ratio Strategy
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**The assignment is to be submitted to Blackboard by June 9th at
11:59PM. Late assignments will be penalized 10% per day**
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Format
1. Include a title page with your name and student number.
2. Given the nature of the accelerated summer course, emphasis will be placed
on producing a short, succinct paper where the focus is on not only
producing the correct answers but the proper interpretation.
3. Your report should not exceed 7 pages (1.5 spaced, TNR, 12 font, including
appendices).
4. Ideally your references should be in APA style. Ideally, I am looking for a
minimum of 6 peer reviewed references (books are acceptable). No webbased
material please (unless WHO or similar sources) (1 mark).
Introduction
While under British rule, visitations from the plague have been an uncommon
occurrence in Maltese Islands. The epidemic of 1813 was most notable in severity,
and scale with nearly 5000 people succumbing from the disease. Other outbreaks
occurred in 1844, 1910, 1919, and 1936/37 but never of the same scale and
magnitude.
To illustrate epidemiological principles and reasoning, this exercise will focus on a
recent outbreak that struck the islands just after WWII. The outbreak of 1945/46
began in June of 1945 and lasted nearly a year. The Bubonic plague here is typically
transmitted by rat-fleas. It was presumed at the time that the disease was one of
importation through maritime activity.
ANTC67
Summer 2017
L. Tripp
2
The Problem
The exercise focuses on the plague and lecture material have provided you with
solid grounding on the subject. Your problem set consists of an outcome variable
and two potential risk factors (Garbage Removal (yes/no), Location
(city/rural/port).
1. Plague Status: case / no case – Outcome
2. No Garbage Removal: Yes/ No – A risk factor
3. Region: Port city/ Inland city/ Rural village – A risk factor
While the above risk factors are perhaps obvious, a search of the literature must be
undertaken to justify the veracity of these risk factors scientifically. If contradictory
support is located, that also acceptable.
Here is a link to a useful reference, to help you get started:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2235074/pdf/jhyg00178-0018.pdf
Introduction (0.5 pg.)- (2 marks)
Include background information on your topic. What is the subject?
a. Describe bubonic, risk factors and why the factors are relevant.
What is the purpose/objective of this report?
Materials & Methods (0.5 pg.) – (2 marks)
At least 2 references should be included in this section.
Outline the exact procedures for obtaining the results. Make use of scholarly
references when answering the questions below:
a. What program(s) did you use? What are the statistical analyses that you
performed? Give a brief description (include equations)/definitions and
explain why you have used these statistics.
ANTC67
Summer 2017
L. Tripp
3
Results (max. 1.5-2pgs.) – (12 marks)
Interpretation of the results/output should be discussed in the body of the text.
Show calculations, tables and figures in appendices (for example, place organized
output/results in tables. Show sample manual calculations for either question 1 or
2).
Part I. Simple Analysis of Relationships-(7 marks)
Assess the overall relationship of Risk factor using a non-stratified analysis. For 1
and 2 provide the following: The Crude Odds Ratio; The Confidence Limits (lower &
upper 99% limits, note not 95%) of OR; MH Chi Square value; and finally, the
interpretation of questions 1 and 2 using the above values.
1. What is the overall relationship of garbage removal and plague status
(irrespective of location)?
2. What is the overall relationship of location and plague status (irrespective of
garbage removal)?
3. What is the overall relationship of garbage removal and location
(irrespective of plague status)? Note, with the two variables it is best to view
the Odds Ratio as a simple chi-square test of association, as there is no
disease outcome.
Part II. Complex Analysis – (5 marks)
a. MH summary ORs, and Interpretation
b. Stratum specific Odds Ratios, Interaction Chi squares, and Interpretation
Discussion: Future Research and final conclusions (1pg.)- (4 marks)
Discuss in two short paragraphs.
a. Identify three “other” factors that may have played a role in plague
resistance/susceptibility. References are necessary. (2 marks)
b. Identify methodological, and other additional limitations that have prevented
you from resolving the complex nature of resistance/susceptibility. (2
marks)
ANTC67
Summer 2017
L. Tripp
4