Quisitor - Take Quiz

21

Multiple Regression Analysis

With regards multiple regression analysis, which of the following statements is/are correct?

It allows us to determine the association between multiple independent variables and outcome

Independent variables may be continuous or categorical

Logistic regression is used when the outcome variable is binary (i.e. present/absent)*

Linear regression# is used when the outcome variable is continuous

All of the above

22

Table 2 - Multiple Logistic Regression analysis for CAD:

With regards Table 2, which of the following statements is/are correct?

Compared with male sex, female sex is protective against CAD.

Every one year increase in age is associated with a statistically significant increase in CAD risk.

After controlling for the effect of sex and age, patients with CAD are 1.2 times more likely to have hypertension than controls (those without CAD).

There is 95% confidence that the true adjusted odds ratio for hypertension is in the interval 1.1 to 1.3

All of the above

23

With regards Table 2, what is the p value of the adjusted odds ratio for female sex likely to be and why?

P value likley to be 1 exactly, as the OR is adjusted for other covariates

0.05 < p < 1.0 because the 95% CI around the adjusted OR does not include the no-effect value of zero.

P likely < 0.05 because the 95% CI around the adjusted OR does not include the no-effect value of zero.

P likely < 0.05 because the 95% CI around the adjusted OR does not include the no-effect value of one.

None of the above

24

Clinical Trial Profile and Loss to Follow-up

Questions 24 to 26 inclusive are related to the following information and Figure 7.

The trial profile in Figure 7 comes form a randomised controlled trial of compression stockings vs no stockings for prevention of symptomless DVT in long-haul flights. (Scurr et al. The Lancet 2001;357:1485)

Figure 7 - Trial profile:

With regards the Trial Profile (Figure 7), which of the following statements is/are correct?

The number of patients lost to follow-up was almost the same in both groups.

The % loss to follow-up in each group is within the expected range for a randomised controlled trial.

Loss to follow-up will not pose a threat to the validity of the findings of this study.

a and b

b and c

25

There were 12 DVTs in the control group and no DVTs in the stocking group. In a worst case scenario analysis performed in order to quantify the potential impact of loss to follow-up on the findings of the study, what would be the incidence rate of DVT in each group?

DVT incidence rate 12/116 in no-stocking and 0/115 in stocking group.

DVT incidence rate 12/116 in no-stocking and 15/115 in stocking group.

DVT incidence rate 28/116 in no-stocking and 0/115 in stocking group.

DVT incidence rate 28/116 in no-stocking and 15/115 in stocking group.

None of the above

26

Regarding an intent-to-treat (ITT) analysis, which of the following statements is/are correct?

It is done to reduce selection bias due to loss to follow-up / noncompletion

In this case, the analysis would include 116 patients in the control group and 115 patients in the stocking group

In this case, the analysis would include 100 patients in the control group and 100 patients in the stocking group

a and b

a and c

27

Survival Analysis

The information below and Figure 8 relate to questions 27 to 30.

A randomised controlled trial was undertaken to compare the efficacy and safety of open versus endovascular repair of abdominal aortic aneurysm. Kaplan Meier (K-M) survival analysis on an intention-to-treat basis was undertaken to compare outcomes in the two groups. For the outcome ‘survival free of severe events’ K-M survival curves for the two groups are presented in Figure 8.

Figure 8:

At the commencement of the study, how many patients were randomly assigned to each of the open and endovascular repair groups?

178 assigned to open and 173 assigned to endovascular repair.

150 assigned to open and 155 assigned to endovascular repair.

146 assigned to open and 151 assigned to endovascular repair.

121 assigned to open and 125 assigned to endovascular repair.

89 assigned to open and 91 assigned to endovascular repair.

28

After 12 months of follow-up, what was the cumulative probability of survival in the open repair group?

Approximately 90%

Approximately 85%

Approximately 100%

Approximately 95%

None of the above

29

At each time point, what constitutes the ‘number at risk’ in each group?

Those still alive

Those still alive and free of severe events

Those still alive, free of severe events and still in study

Those still alive, free of severe events or lost to follow-up

None of the above

30

Which of the following statements is/are correct?

The survival curves start to diverge early in follow-up, around the 2-3 month mark

Based on p=0.39, there is no statistically significant difference in the survival of patients, free of severe events, over the two years of follow-up

This study is susceptible to sampling selection bias as the patients in this study may not be representative of all patients undergoing AAA repair

This study is susceptible to bias through loss to follow-up

All of the above

HP3 Quiz 3 Practice

21

Multiple Regression Analysis

22

23

24

Clinical Trial Profile and Loss to Follow-up

25

26

27

Survival Analysis

28

29

30