Institute of Public Health

Institute of Public Health

Master of Public Health (MPH) Programme

Clinical Epidemiology and Chronic Disease Epidemiology
CMPH 626 0 CRN: 24043
Assessment Workbook

June 2014

Institute of Public Health ? College of Medicine & Health Sciences (FMHS)
UAE University ? PO Box 17666 ?Al Ain, United Arab Emirates
Tel: +971-3-7137-483 (Secretary) ? Fax: +971-3-767-2022 ?
Website: http://www.cmhs.uaeu.ac.ae/en/depart/iph/

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For this assessment you are required to read the information provided, research any terminology used or information presented that you do not currently understand and then answer the following questions.

This assignment contains seven (7) questions and constitutes 75% of the module. A total of 100 marks are available for this assignment and the marks for each individual question are clearly stated. Recommended time to complete the assignment is 5 hours (excluding reading and research). Answer each question in about 100-300 words (depending on detail of answer required), use Font size 11. Do not type outside the boxes provided. Do not cut and paste.

Question 1 (12 marks)
Choose three diseases or conditions within a specific setting (i.e. place or population group) of which you have some knowledge. Try to select contrasting conditions, such as conditions affecting different age groups or of particular importance in different parts of the world. Using the following matrix, for each condition you have chosen, list the determinants under each of the six categories shown in the matrix. Complete as many as seem appropriate.
(four marks for each condition).

1 2 3
Disease or condition
Setting

Determinants
Age, sex, genes:
Individual behaviours:
Community and social networks:
Living and working conditions:
Broader socio-economic and environmental factors:
Globally operating factors:

Question 2 (18 marks)
Select a chronic disease of your choice and write short notes on its Epidemiology using the headings shown below. (two marks for each part)

1. Public health significance

2. Patho-physiology
3. Descriptive epidemiology

4. Causes
5. Prevention and control
6. Screening
7. Treatment
8. Examples of evidence based interventions
9. Areas for future research
Question 3 (13 marks)
You are the head of an emergency department. Your department is seeing an increasing number of patients who are HIV positive. After doing a preliminary cross-sectional survey to assess the main types of sharps injury in the clinic, you realize that needle stick injuries from blood drawing are frequent among nursing staff and that injuries from suture needles are most frequent among doctors. You decide that you need to implement a comprehensive programme of sharps injury prevention to protect your staff, using Haddon’s injury matrix as a guide to different countermeasures.
Part A.
Complete the row and column headings for your Haddon matrix. (three marks)

Part B.
You persuade the clinic administrator to purchase syringes with retractable needles to protect staff from needle sticks during blood drawing. Place this action in the appropriate cell of the matrix (two marks).

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Part C.
In order to protect doctors from suture needle injuries, you introduce mandatory teaching of essential safe surgical skills for all new doctors, including the use of needle drivers and forceps to avoid touching of needles and wearing of latex gloves. Place this action in the appropriate cell of the matrix (two marks).

Part D.
Think of two other actions that you could take. Describe these actions and place them in the appropriate cell of the matrix (four marks).

Part E.
There are two basic types of safety protection, the wearing of latex gloves is which of these two types? (one mark)
Part F.
The epidemiological triad is a main concept used in injury epidemiology. What is an agent in the needle-stick injury? (one mark)
Question 4 (13 marks)
A study was made of doctors’ ability to diagnose streptococcal infection in 149 patients coming to the emergency department with sore throats. Doctors’ clinical impressions were compared to results of throat cultures for the bacterium Group A streptococcus. Thirty-seven patients had positive throat cultures, and 27 of these were diagnosed by doctors as having strep throat. One hundred twelve patients had negative cultures, and doctors diagnosed 35 of these as having strep throat.

One mark for Each Question
1. In this study what diagnostic test is being evaluated?
2. In this study what is the Gold Standard?
3. What is the sensitivity of the doctors’ clinical impression of strep throat in this study?
4. What is the specificity?
5. If the doctor thought the patient had strep throat, for what percent of patients was she correct?
6. If the doctor thought the patient did not have strep throat, for what percent of the patients was he correct?
7. How common was strep throat in patients coming to the emergency department?
8. What is the Likelihood Ratio of a positive test (ie. the doctor deciding on clinical grounds that a patient has strep throat)?
9. Describe in your own words how you interpret this Likelihood Ratio

10. What is the accuracy of the clinical impression of doctors about whether a patient has a strep throat?
11. If the doctors knew results of the throat cultures when recording their clinical impressions what effect would this have on the results of this study

12. If only some patients attending the ER with sore throat got throat cultures, what effect would this have on the results of this study.

13. Based on these findings, what advice would you give to the ER doctors about taking throat cultures from patients with sore throat.

Question Five (16 marks)
Read the following abstract which summarises a prognostic study.
There is limited knowledge on prognostic factors for developing chronic low back pain (LBP) at an early stage of LBP. The objectives of this study were to investigate the clinical course of pain and disability, and prognostic factors for non-recovery after 1-year, in patients seeking help for the first time due to acute LBP. An inception cohort study included 123 patients with acute LBP lasting less than 3 weeks and consulting primary care for the first time. Main outcome measures were pain intensity, Roland-Morris disability questionnaire (RMQ), and sickness absence. Eleven patients (9%) did not return for the 12-month follow-up. There were large and significant reductions in pain intensity (P<0.001) and RMQ scores (P<0.001) during follow-up. Patients with neurological signs showed significantly less improvement in pain (P=0.001) and RMQ (P=0.004) compared with those without neurological signs. The proportions with sickness absence due to LBP at 6, 9, and 12 months were 7%, 8%, and 9%, respectively. At 12 months, 17% of patients had not fully recovered. Multivariate logistic regression analyses showed that high scores on a psychosocial screening (acute low back pain screening questionnaire) and emotional distress (Hopkin’s symptom check list) were significantly associated with non-recovery at 12 months, with odds ratios of 4.4 (95% confidence interval 1.1-17.4) and 3.3 (1.1-10.2), respectively.
Grotle M, Brox JI, Glomsrød B, Lønn JH, Vøllestad NK. Prognostic factors in first-time care seekers due to acute low back pain. Eur J Pain 2007; 11(3):290-8.
Write 1-2 sentences on each of the following (two marks for each section)
1. Was the sample of patients assembled in an appropriate way?
2. How representative is the sample?
3. Was patient follow-up sufficiently long and complete?
4. What were the outcome criteria, were these objective and applied in a ‘blind’ fashion?
5. What different prognostic factors were identified and how did adjustment for these take place?

6. What are the results?
7. How precise are the prognostic estimates?
8. Your brother telephones to say that he has suddenly developed back-pain for the first time. Can you use the results of this study to advise him? If so what will you say?

Question 6 (Total of 15 Marks Available)
Clinical Trials
Please read the following extract from the Thompson et al. (2010) article published in the Journal of Applied Physiology (108:769-779).
Time course of changes in inflammatory markers during a 6-mo exercise intervention in sedentary middle-aged men: a randomized-controlled trial
Study Background:
• Chronic low-grade inflammation plays a central role in the aetiology of diseases such as cardiovascular disease
• Regular exercise may improve systemic markers of chronic inflammation, but direct evidence and dose-response information is lacking
• Observational research provides evidence for a strong inverse relationship between physical activity/fitness and serum markers of inflammation (e.g. IL-6, CRP)
• Causal evidence from experimental studies provides less consistent evidence as a number of short-term (1-3 months) and longer-term exercise interventions (6-10 months) have shown either a positive impact or no impact on markers of inflammation
• Limitations to these experimental studies include a lack of control group, failure to assess compliance with the prescribed exercise intervention, and poor measures of physical activity.
Study Aim:
The primary aim of the present randomised-controlled trial was to examine the effect of a 6 month exercise intervention on the magnitude and time course of changes in markers of low-grade inflammation in sedentary middle-aged men.
Materials and Methods:
Participants.
Sedentary male volunteers (aged 45–64 yr) were recruited from the local community. A total of 152 telephone screening interviews were conducted (Fig. 1). Individuals with known disease (e.g., heart disease, diabetes, arthritis) or who self-reported they engaged in structured physical activity lasting =30 min on two or more occasions per week were excluded from the study, as were volunteers who smoked, had a body mass index (BMI) =35 kg/m2, or took regular medication. Eligible participants completed a health questionnaire and were fitted with a physical activity monitor to further establish that they were sufficiently inactive, before being randomly allocated to one of two groups using a sealed envelope (Fig. 1). The envelopes were numbered with the sequence generated and known only by a third party. Each volunteer provided written informed consent, and the investigation was approved by the local ethics committee.

Study design.
Parallel group, randomised controlled trial. Participants in both groups reported to the laboratory at baseline and then 4, 12, and 24 later, each time following a 12-h overnight fast.
Exercise intervention and control.
Individuals in the exercise group completed a 24-wk exercise training program. Intensity and duration were increased in a progressive manner. The exercise (attendance, exercise duration, and heart rate) was recorded using a monitoring system (Fitronics, Bath, UK). Once every fortnight, volunteers reported to the laboratory to complete one of their weekly exercise sessions so that intensity and heart rate response could be monitored and the exercise prescription altered accordingly. Men in the control group were asked to maintain their current lifestyle and levels of physical activity during the 26-wk study period.
Figure 1: Flow of participants through the study

Total of 15 marks available.

1. Figure 1 shows the Flow of Participants through the study. One-hundred and fifty-two middle-aged men were assessed for eligibility and 95 males were excluded from the allocation phase as they did not satisfy the inclusion criteria. Using the data presented in Figure 1, calculate the percentage of participants from the study population which formed the study sample. (1 mark)
2. State one possible reason why individuals on regular medication were excluded from the study? (1 mark)

3. State the two screening methods used to ensure that all participants in the study sample were classified as ‘sufficiently inactive’ prior to group randomisation (2 marks)

4. Define the term compliance and state which type of bias it is related to? (2 marks)

5. Describe how the authors assessed compliance to the exercise intervention (1 mark)

During the Journal of Applied Physiology’s peer review process, one of the reviewers suspects that the randomisation was not conducted blindly and that the member of the study research team responsible for the group randomisation process allocated the more physically inactive (i.e. sedentary) middle-aged males preferentially to the treatment (exercise intervention) group.

6. What is the gold standard method of group randomisation in a randomised-controlled trial? (1 mark)

7. State one reason why using a non-random group allocation procedure might distort the ‘true’ effect of the exercise intervention? (1 mark)

8. Which type of bias is associated with a failure to randomise participants? (1 mark)

9. Which statistical test could the study researchers perform to provide evidence that group allocation was random? (1 mark)

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10. What does the term blinding mean? (1 mark)

11. Why was it not possible to blind study participants to group allocation? (1 mark)

12. Using the data presented in Figure 1, state the total number of participants that would be involved in the following analyses:

(i) Intention to treat analysis (1 mark) =

(ii) Per-protocol analysis (1 mark) =

Question 7 (Total of 13 Marks Available)
Systematic Reviews and Meta-Analysis
Please read the following abstract from a systematic review and meta-analysis conducted by Umpierre and colleagues which was published in the Journal of the American Medical Association. 2011;305(17):1790-1799):
Abstract
Physical activity advice only or structured exercise training and association with HbA1c levels in type 2 diabetes. A systematic review and meta-analysis
Note: Glycated hemoglobin (HbA1c) is a blood marker used to monitor blood glucose levels. Higher amounts of HbA1c indicate poorer control of blood glucose and have been associated with cardiovascular disease in type 2 diabetes patients. The American Diabetes Association Standards of Medical Care in Diabetes 2011 guidelines state HbA1c =6.5% the criterion for the diagnosis of diabetes.
Context: Regular exercise improves glucose control in diabetes, but the association of different exercise training interventions on glucose control is unclear.
Objective: To conduct a systematic review and meta-analysis of randomized controlled clinical trials (RCTs) assessing associations of structured exercise training regimens (aerobic, resistance, or both) and physical activity advice with or without dietary co-intervention on change in hemoglobin A1c (HbA1c) in type 2 diabetes patients.
Data Sources: MEDLINE, Cochrane-CENTRAL, EMBASE, ClinicalTrials.gov, LILACS, and SPORTDiscus databases were searched from January 1980 through February 2011.
Study Selection: RCTs of at least 12 weeks’ duration that evaluated the ability of structured exercise training or physical activity advice to lower HbA1c levels as compared with a control group in patients with type 2 diabetes.
Data Extraction: Two independent reviewers extracted data and assessed quality of the included studies.
Data Synthesis: Of 4191 articles retrieved, 47 RCTs (8538 patients) were included. Pooled mean differences in HbA1c levels between intervention and control groups were calculated using a random-effects model. Overall, structured exercise training (23 studies) was associated with a decline in HbA1c level (-0.67%; 95% confidence interval [CI], -0.84% to -0.49%; I2, 91.3%) compared with control participants. In addition, structured aerobic exercise (-0.73%; 95% CI, -1.06% to -0.40%; I2, 92.8%), structured resistance training (-0.57%; 95% CI, -1.14% to -0.01%; I2, 92.5%), and both combined (-0.51%; 95% CI, -0.79% to -0.23%; I2, 67.5%) were each associated with declines in HbA1C levels compared with control participants. Structured exercise durations of more than 150 minutes per week were associated with HbA1c reductions of 0.89%, while structured exercise durations of 150 minutes or less per week were associated with HbA1C reductions of 0.36%. Overall, interventions of physical activity advice (24 studies) were associated with lower HbA1c levels (-0.43%; 95% CI, -0.59% to -0.28%; I2, 62.9%) compared with control participants. Combined physical activity advice and dietary advice was associated with decreased HbA1c (-0.58%; 95% CI, -0.74% to -0.43%; I2, 57.5%) as compared with control participants. Physical activity advice alone was not associated with HbA1c changes.
Conclusions: Structured exercise training that consists of aerobic exercise, resistance training, or both combined is associated with HbA1c reduction in patients with type 2 diabetes. Structured exercise training of more than 150 minutes per week is associated with greater HbA1c declines than that of 150 minutes or less per week. Physical activity advice is associated with lower HbA1c, but only when combined with dietary advice.

Total of 14 marks available.
13. Read the abstract and state two inclusion criteria for studies to be selected for the systematic review (2 marks).

i.

ii.
14. During the ‘Data Extraction’ phase of the study two independent reviewers extracted data and assessed quality of the included studies. Why? (1 mark)

15. Name two potential sources of bias related to the literature search (2 marks)

i.
ii.
16. State one strength and one limitation of a meta-analysis? (1 mark)

Strength:
Limitation:
17. Which test can be used to determine the presence of heterogeneity in a meta-analysis? (1 mark)

18. In the ‘Data Synthesis’ section of the abstract the authors state that “pooled mean differences in HbA1c levels between intervention and control groups were calculated using a random-effects model.” What is the main assumption of a random effects model? (1 mark)

19. The authors provide details of which databases were used during the literature search to find published articles. Name one method of obtaining unpublished literature. (1 mark)

20. Which type of graph can be used to assess publication bias in a meta-analysis? (1 mark)

21. Look at the Forest Plot displayed in Figure 1 (below). Three studies (Raz et al., 1994; Vancea et al., 2009c; Vancea et al., 2009d) appear to have wide confidence intervals which cross the line of unity, what does that suggest about the results of those individual studies? (1 mark)

22. Based on the results in the ‘Data Synthesis’ section of the abstract and the Forest plot presented in Figure 1 (below), which type of exercise training (i.e. aerobic, resistance, or combined aerobic and resistance training) and duration (minutes per week) would you prescribe to a diabetes patient looking to maximise the beneficial effects of exercise training on HbA1c? (2 marks)

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