STAT6000 Epidemiology and Evidence
Assessment 3
Question I (13 Marks)
1. Read the following article by Cao et al., “Cao Y, Zhao S, Bexelius TS, Söderling J, Shi M, Roelstraete B, Warner BB, Stephansson O, Ludvigsson JF. Pregnancy and neonatal outcomes among women with early-onset colorectal cancer: a nationwide case–control study. Eclinicalmedicine. 2023 1;59 (https://doi.org/10.1016/j.eclinm.2023.101963) and answer the following questions related to the risk of adverse pregnancy and neonatal outcomes among women with early-onset colorectal cancer.
1.1. What are the cases and controls in the study and what is the definition of a case and a control? [4 marks].
Answer:
1.2. Refer to Table 2 on page 6 of the article, and use the numbers reported in the table to construct a 2×2 table with ‘Gestational diabetes’ as the exposure variable and ‘births in women with colorectal cancer’ as the outcome variable. [1 mark]
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1.3. Refer to Table 3 on page 6 of the article and identify the independent variable(s) that are statistically significantly associated with the outcome variable. Justify your identification of their significance association. Of these significantly associated variables, which one of the variables has a strong association and why? [3 marks]
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1.4. Which challenges did the authors (or can you) identify that could potentially lead to bias and why? [3 marks]
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1.5. List and discuss the strengths of a case-control study design against a cohort study design in exploring the relationship between risk of adverse pregnancy and neonatal outcomes among women with early-onset colorectal cancer. [2 marks]
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Question II [9 marks]
2. Read the following article by Blackmore, R., et al. “Blackmore R, Boyle JA, Fazel M, Ranasinha S, Gray KM, Fitzgerald G, Misso M, Gibson-Helm M. The prevalence of mental illness in refugees and asylum seekers: A systematic review and meta-analysis. PLoS medicine. 2020 Sep 21;17(9):e1003337” (https://doi.org/10.1371/journal.pmed.1003337) and answer the following questions related to prevalence of mental illness in refugees and asylum seekers.
2.1. Identify the research questions using a PICO (Population-Intervention-Comparison-Outcome) approach? [2 mark]
Answer:
2.2. Was there a significant heterogeneity across studies in the prevalence of depression? Explain why or why not? [5 marks]
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2.3. Was there a publication bias for psychosis? Explain why or why not? [2 marks]
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Question III [8 marks]
3. Read the following article by Figueiredo, “Figueiredo AC, Gomes-Filho IS, Batista JE, Orrico GS, Porto EC, Cruz Pimenta RM, dos Santos Conceição S, Brito SM, Ramos MD, Sena MC, Vilasboas SW. Maternal anemia and birth weight: A prospective cohort study. PloS One. 2019 Mar 18;14(3):e0212817” (https://doi.org/10.1371/journal.pone.0212817) and answer the following questions related to the association between maternal anemia and low/insufficient birth weight.
3.1. Identify the exposure(s) and outcome of the study? [1 mark]
Answer:
3.2. Refer to Table 2 on page 7 of the article, and use the numbers reported in the table to construct a 2×2 Table with ‘Abortion’ as the exposure variable and ‘Maternal anemia’ as the outcome variable and calculate the risk ratio. [2 marks] (Note: In the abortion category ‘yes’ should be positive for the exposure).
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3.3. Let’s assume residence is a potential confounder variable for this study (Figueiredo, A. C. M. G., et al. 2019). How would you manage this confounding variable? Justify your reasoning and provide detail strategies to deal with this confounding variable. [3 marks]
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3.4. Discuss the strengths of using a cohort study design in the article compared to a case-control study design when examining the association between maternal anemia and low/insufficient birth weight. [2 marks]
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Question IV [10 marks]
4. Please read the article by Dequin, Meziani et al., “Dequin PF, Meziani F, Quenot JP, Kamel T, Ricard JD, Badie J, Reignier J, Heming N, Plantefève G, Souweine B, Voiriot G. Hydrocortisone in severe community-acquired pneumonia. New England Journal of Medicine. 2023; 1931-1941.” https://doi.org/10.1056/NEJMoa2215145 about hydrocortisone use in severe community-acquired pneumonia. Please give detailed answers to the following questions based on the paper. Please support your answer with a paragraph and page number from the article.
4.1. Did the study provided a focused and clear research question regarding the population studied, intervention given, comparator chosen, and outcomes measured [4 marks]?
Answer:
4.2. Did the hydrocortisone use among adults in the intensive care unit for severe community-acquired pneumonia significantly improved the death hazard in 28 days? Do you recommend using hydrocortisone for this population? Support your arguments with specific texts from the study (2 marks).
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4.3. Which method was used to assign participants to the intervention and control groups? Did the study groups have similar characteristics at the baseline? What could be the effect of coexisting conditions (COPD, Asma, Diabetes, immunosuppression) if it was higher in the control group than in the intervention group (2 marks)?
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4.4. Did the authors calculate sample size for the study? Which methods of calculation did they use? Was the sample size sufficient for the proposed effect sizes? What could be the effect of using an insufficient sample size (2 marks)?
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Question V [10 marks]
5. Please read the article by León, Vaccaro et al., “León M, Vaccaro H, Alcázar JL, Martinez J, Gutierrez J, Amor F, Iturra A, Sovino H. Extended transvaginal sonography in deep infiltrating endometriosis: use of bowel preparation and an acoustic window with intravaginal gel: preliminary results. Journal of Ultrasound in Medicine. 2014;33(2):315-21.” (https://doi.org/10.7863/ultra.33.2.315) about the validity of transvaginal sonography for endometriosis screening.
5.1. Was there a clear question for the study to address? Please discuss your answer about the population, the screening test, the setting, and the outcomes [4 marks].
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5.2. What was the reference standard diagnostic test? Was it an appropriate standard test [2 marks]?
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5.3. Please calculate Rectosigmoid’s accuracy and positive predictive values and interpret the results. Show the necessary steps in the calculation. Please refer to Table 3 [4 marks].

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