PHCM 9794 : Foundations of Epidemiology Ovarian Cancer in Women - Medical Science Assignment Help

Assignment Task:

Task:

Question 1

 Ovarian cancer in women is difficult to diagnose in the early stages due to vague symptoms that are commonly experienced by women without ovarian cancer. The majority of diagnoses are made at an advanced stage where survival is poor. Ovarian cancer has a 5-year survival rate of 46% and it is estimated that there will be 1,075 deaths from ovarian cancer in Australia in 20191 . A blood test for the protein CA125, which can be produced by ovarian cancer cells, has been suggested as a screening test for ovarian cancer in older women (aged 50 years or more). A CA125 result greater than or equal to 35 U/mL is considered a positive test. A prospective cohort study was conducted with 34,253 women aged 50 years or more, of whom 212 had ovarian cancer at follow-up, and the remaining 34,041 did not have ovarian cancer according to a gold standard test. The CA125 blood test detected ovarian cancer in 73 of the 212 participants with ovarian cancer. Of the 34,041 participants without ovarian cancer, 33,634 tested negative using CA125.

a) Complete a 2 x 2 table of the results of the CA125 test compared to the gold standard. Label your table appropriately. [4 marks]

b) Calculate the sensitivity of the CA125 test. Show your working. [2 marks]

c) Interpret the value you calculated in part (b). [2 marks]

d) Calculate the specificity of the CA125 test. Show your working. [2 marks]

e) Interpret the value you calculated in part (d). [2 marks]

f) If the threshold for testing positive was reduced what impact would this have on sensitivity and specificity? Explain your answer. [2 marks]

g) Considering the values you have calculated in parts b and d, would you recommend its use for population screening? Explain your answer. [3 marks]

h) If a woman in this cohort study had a positive CA125 test how likely is it that they truly have cancer? [4 marks]

i) Describe two other factors (other than sensitivity/specificity) that need to be considered to determine whether a routine ovarian cancer screening program should be implemented for women aged 50 years or more.

Question 2 [30 marks] Read the published study (Jackson et al.). Use the information contained in the paper to answer the following questions. Note that in this study, the investigators use generalised equation modelling. This is a type of regression model that enables adjustment for changes in the study factor and confounders over time (i.e. time varying exposures and co-variates) and reports adjusted values as odds ratios. Time-varying covariates are variables that are not fixed at one point, they may change over the duration of follow-up.

a) What was the research question? Use PECO format if applicable. Was it a descriptive, predictive or causal research question? [3 marks]

b) What type of study was used? Is it an appropriate study design to answer the research question? Give reasons for your answers. [3 marks]

c) Describe the target population, source population and study participants? [3 marks]

d) This question is about selection bias and has two parts. First, describe one approach that the investigators used to minimise selection bias in this study. Include a reason for your answer. Second, describe one issue that may be a source of selection bias in this study. Include a reason for your answer. [4 marks]

e) What was the study factor? How was it collected in participants and how was the exposure measurement developed? [3 marks] a. This question is about measurement error and bias and has two parts. First, describe one approach that the investigators used to minimise measurement error and bias of the study factor. Include a reason for your answer. Second, describe one issue that may be a source of measurement error and bias of the study factor in this study. Include a reason for your answer. [4 marks]

f) What were the outcome factors and how were they measured? [2 marks]

g) Describe two strategies that the investigators used to minimise confounding in this study? What is your assessment of the potential for residual confounding in this study? Give reasons for your answer.

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