Introduction to Clinical Epidemiology


Autumn, 2019

Due date: 11.59pm , May 29 2019

This assignment is based on the learning objectives and concepts as described in the Unit Learning Guide. There are 9 questions worth a total of 64 marks and this assignment will contribute 64% towards the total assessment for this subject.

Your assignment should be typed, with adequate space left between questions. Assignments should be submitted via vUWS. Be as concise as possible in your answers, and use the number of marks allocated to each question as a guide for how much to write.

Please note this is an individual exercise.

Late assignments will not be accepted without prior approval.

You are required to answer ALL questions (1-9)

Page 1 of 7

Answer questions 1-2 based on the following scenarios:

Q1: Fred, a 65-year-old obese man with a history of type 2 diabetes mellitus and hypertension presents to the GP practice for a follow-up appointment. During the consultation, he asks whether there is a better medication to glicazide and metformin, his oral hypoglycemic medications, which he has been taking to control his blood sugar. His friend has recently been put on a newer oral hypoglycemic medication (Liraglutide, a glucagon-like peptide-1 analogue), which has been shown to help with weight management in patients with diabetes and obesity. Fred has been finding it very difficult to lose weight for a few years now as he has tried various lifestyle modifications. He asks whether the new oral hypoglycemic medications could be an option for him in weight reduction.

Task [2 marks]

a. Write a focused research question for this particular problem that will help you organise a search of the literature for an answer (use the PICO elements as appropriate).

b. Identify the PICO elements in your research question

Q2: In the past 2 years, as an Infectious Disease Specialist in one of the tertiary hospitals in Australia, you have attended to 23 migrant patients who were referred by their General Practitioners with symptoms not typical of pulmonary tuberculosis. After taking a detailed history and performing appropriate physical examinations, as well as reviewing a range of relevant investigations, you clinically diagnosed and microbiologically confirmed that those patients have multi-drug resistance pulmonary tuberculosis (MDR-TB). The Public Health Department was notified of disease and the patients were managed accordingly. Now, you and some colleagues from Western Sydney University want to investigate the risk factors for MDR-TB.

Task [2 marks]

a. Write a focused research question for this particular problem that will help you organise a search of the literature for an answer (use the PICO elements as appropriate).

b. Identify the PICO elements in your research question

Q3: Please select the single best answer for each of questions 3.I – VII

I. Randomised controlled trials provide strong evidence that an observed effect is due to the intervention. One main reason is because [1 mark]:

a) When the study participants are randomised, many characteristics and potential confounders are likely to be evenly distributed in the groups

b) It is easier to measure the outcome variable with great precision in randomised controlled trials compared to other study designs.

c) The exposure level and the outcome are measured at the same time

d) The study participants are volunteers and therefore motivated to take part in the study

e) None of the above

II.Blinding is an important feature of a randomised controlled trials because [1 marks]:

a) It helps prevent measurement bias – the biased assessment of outcomes

b) It helps reduce contamination and compliance problems

c) It helps reduce confounding and selection bias

d) It is required to do an intention-to-treat analysis

e) It helps improve chance event and reduce misclassification III. Which of the following is true [1 mark]?

a) Loss to follow-up can lead to selection bias in cohort studies.

b) Selection bias can arise from conditioning on the common effect of the exposure and an uncontrolled independent risk factor for the outcome.

c) Case-control studies are no more prone to selection bias than are cohort studies.

d) Loss to follow-up is not a major source of bias in cohort studies.

e) None of the above.

IV. When epidemiologists judge the evidence to establish a possible cause of a health outcome, they

consider [1 mark]:

a) The strength of the association between an exposure and the outcome

b) Evidence that the exposure of interest has appeared before the outcome.

c) Evidence showing that reductions in the exposure level will reverse the risk of the outcome.

d) A, B and C

e) A and B only

V. A double-blind study was designed to test the efficacy of a drug. One group of the patients consisting of 1227 participants were given a placebo and the other group of patients consisting of 1220 were given the active drug. Both groups were to be followed up for one year. After 6-months of the trial, 35% of participants in the placebo groups dropped out of the study and 4% of the participants taking the active drug dropped out of the study. What is the SINGLE BEST explanation for this occurrence [1 mark]?

a) Failure of the active drug

b) Insufficient information to interpret data

c) Systematic error

d) Chance event

e) Breakdown of the double-blind study

VI. The highest level of evidence provided for cancer treatment usually comes from: [1 mark]

a) Randomised control trials

b) Phase II clinical trials

c) Phase III clinical trials

d) Systematic reviews of observational studies

e) Meta-analyses of intervention studies

Page 3 of 7

VII. A recent study examined the association between tea consumption and ovarian cancer. The study included 414 women with primary epithelial ovarian, fallopian, or peritoneal cancer and 868 age-and region-matched women with non-neoplastic conditions. The adjusted odds ratio was 0.39 for those drinking tea daily and 0.23 for those drinking tea for 30 years, compared with non-tea drinkers. The study concluded that increasing frequency and duration of tea drinking, especially green tea, can reduce the risk of ovarian cancer.

What type of study was conducted? [1 mark]

a) Cross-sectional study

b) Prospective cohort study

c) Randomised controlled trial

d) Retrospective cohort study

e) Case control study

Q4: Now select ONLY ONE research question from either Question 1 or 2 above that will help you organize a search of the clinical literature for an answer. If you were to search Medline/PubMed/Web of science for original research on this question:

a. Describe what your search strategy would be, including keywords, MeSH terms, inclusion and exclusion criteria, as well as evidence of the Boolean operators used [4 marks].

b. What type of study design would best be able to address your selected research question? State why [1 mark].

c. Cite the best article from among those you find, using any referencing style of your choice [1 mark].

Q5: Answer questions 5a-b based on the following information:

A total of 1800 patients have a screening test to identify a protein called “FEN-59’ to determine patients at risk of lung carcinoma, followed by a standardized lung biopsy procedure. Of the 1800 children, 1533 have a negative FEN-59 and 267 have a positive FEN-59. In addition, a lung biopsy (gold standard) was done on all patients. Of those patients with a negative FEN-59, 1491 have a negative lung biopsy. In the group with a positive FEN-59, 259 have a positive lung biopsy.

Construct a 2×2 table using the information provided above, and answer the following questions (a and b):

a) Calculate the sensitivity of the FEN-59 [2 marks]

b) Calculate the positive predictive value of the FEN-59 [2 marks]

c) The negative predictive value is dependent on all of the following: prevalence, incidence, sensitivity and specificity [True/False] [1 mark]

Please select the SINGLE BEST answer in questions 5e to f

d) Using the image below, which value in the test result units is the point of maximum specificity? [1 mark]

a) 30

b) 15

c) 5

d) 20

e) 25

e) A study was conducted in which 10,000 women participated. All women underwent a cervical smear. 1,000 of 10,000 women had a positive smear. Of these, 100 developed cervical cancer. 10 women who had negative smear developed cancer. What is the SINGLE most likely terminology to describe the 10 women with negative results who developed cervical cancer?

[1 mark]

a. True negative

b. False negative

c. True positive

d. False positive

e. Chance event

Q6: Answer questions 6a-d based on the following information:

You have brought to the attention of the hospital medical services that a published trial reported reduced body weight in patients with morbid obesity who were treated with liraglutide, a glucagon-like peptide-1 equivalent. You mentioned this published paper to your Director, and given the evidence reported, he asked you to give a presentation about the study findings during the weekly seminar series. In your presentation, she has asked you to address the following questions (6a-d) based on the results of the published paper (Edited abstract is shown below):

A Randomized, Controlled Trial of 3.0 mg of Liraglutide in Weight Management (Xavier Pi-Sunyer, M.D., Arne Astrup, M.D., D.M.Sc., Ken Fujioka et al. N Engl J Med 2015;373:11-22.

DOI: 10.1056/NEJMoa1411892)

Background: Obesity is a chronic disease with serious health consequences, but weight loss is difficult to maintain through lifestyle intervention alone. Liraglutide, a glucagonlike peptide-1 analogue, has been shown to have potential benefit for weight management at a once-daily dose of 3.0 mg, injected subcutaneously.

Methods: We conducted a 56-week, double-blind trial involving 3731 patients who did not have type 2 diabetes and who had a body-mass index of at least 30 or a BMI of at least 27 if they had treated or untreated dyslipidemia or hypertension. We randomly assigned patients in a 2:1 ratio to receive once-daily subcutaneous injections of liraglutide at a dose of 3.0 mg (2487 patients) or placebo (1244 patients); both groups received counselling on lifestyle modification.

Results: At week 56, patients in the liraglutide group had lost a mean of 8.4±7.3 kg of body weight, and those in the placebo group had lost a mean of 2.8±6.5 kg (a difference of -5.6 kg; 95% confidence interval, -6.0 to -5.1; P 0.001). A total of 63.0% of the patients in the liraglutide group as compared with 37.0% in the placebo group lost at least 5% of their body weight (P 0.001).

Conclusion: In this study, 3.0 mg of liraglutide, as an adjunct to diet and exercise, was associated with reduced body weight and improved metabolic control.

Q6a. Construct a 2×2 table using relevant figures shown in the abstract, and answer the following questions: [4 marks]

(i) What is the risk of losing at least 5% of body weight in all patients included in the study?

(ii) What is the risk of losing at least 5% of body weight in patients who were treated with liraglutide?

(iii) What is the risk of losing at least 5% of body weight in patients who were treated with placebo?

(iv) What is the relative risk of treatment with liraglutide verus placebo with regard to weight management? How would you interpret this relative risk estimate?

Q6b. If equal numbers of patients in the population were treated with liraglutide vs placebo treatment, what would be the expected population relative risk reduction (RRR) for liraglutide treatment? How would you interpret this measure? [4 marks]

Q6c. How many patients need to be treated with liraglutide for one more patient to benefit compared with the placebo? What is this measure called? How would you interpret this measure [4 marks]?

Q6d. How does the measure in question 5b differ from question 5c? [4 marks]

Read the attached original research article (Khorana et al., 2019), available in vUWS), and now answer Questions 7 to 9:

Q7. What characteristics of the study would you consider in order to determine if its findings are valid? Include wider considerations of study quality/validity and give examples. (Q8 will address relevance, and the next question will ask how to determine the importance of the findings…for this question, focus on the internal validity of the study) [8 marks]

Q8. What characteristics of the findings would you consider, in order, to determine if they are clinically meaningful and statistically significant? Include examples. (You’ve already addressed validity…for this question, focus on how to determine the clinical significance and statistical significance of an effect reported in the study) [8 marks]

Q9. What characteristics of the study would you consider, in order, to determine if it is generalizable to your context? Explain your answers and provide examples. (Questions 6 and 7 have asked how to determine if the study is valid, and how important the findings are….for this question, focus on how to determine if it is really relevant or generalizable to your practice.) [8 marks]


0 Please do not list the characteristics in questions 8–10, but explain your answers succinctly.

0 You can also download the article from the University Library using your student login details.

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