Research & Epidemiology

Question 1

Elements of foreground questions for specific knowledge to inform clinical decisions or actions:

Answer 1

PICO letters stand for:
P: Patient or population. The first step in the PICO process is to identify the patients or population to be studied. More specifically, it describes patients‟ characteristics, such as age, gender, disease status, or any other patientrelated characteristic.
I: Intervention to be tested. Identifying the intervention is the second step in the PICO process. It is important to identify the exposure intended to be studied in the research project. This may include the use of a specific diagnostic test, treatment, adjunctive therapy, medication, etc.
C: Comparison used in the research project. It is the alternative exposure to which the intervention will be compared, which might be the standard of care or a placebo. The comparison component is the only optional one in the PICO question, since the researcher might study the intervention alone because either due to no interest in comparison or the lack of a comparable group.
O: Outcome to be measured as a result of the intervention. It is the evaluation of the intervention‟s effect. This may include cure or level of control of a disease, efficacy of a medication or a diagnostic test, etc.

Question 2

Odd ratio used in which study ?

Odd ratio for

Answer 2

case-control but if difference is small, odds ratio will be useful for all (cohort,RCT,case-control)

Question 3

Sensitivity equation:

Answer 3

True Positives/(true positives + false negatives)

Question 4

False Positive Rate:

Answer 4

1 − specificity

Question 5

False Negative Rate:

Answer 5

1 − sensitivity

Question 6

Specificity equation:

Answer 6

True Negatives/(true negatives + false positives)

Question 7

Positive Predictive Value:

Answer 7

True Positive/(true positive + false positive)

Question 8

Negative Predictive Value:

Answer 8

True Negative/(true negative + false negative)

Question 9

What is the best design you choose to study the

prevalence of a disease?

Answer 9

Cross sectional study

Question 10

What is the best trial design to study the incidence of

a disease?

Answer 10

Cohort study

Question 11

Which of the following studies is considered a gold

standard for analytical epidemiology?

Answer 11

Cohort study

Question 12

A critical appraisal of a RCT takes into consideration the followings:

Answer 12

A- Randomization
B- Blinding
C- Precision of the estimate (CI)
D- Benefice versus harm

Question 13

In External validity to check the Applicability of results to your patients several Issues needed to consider before deciding to incorporate research evidence into clinical practice which are …

Answer 13

• Similarity of study population to your population
• Benefit versus harm
• Patients preferences
• Availability
• Costs

Question 14

The best type of study to evaluate a therapy or screening ?

Answer 14

Clinical trials

Question 15

The best type of study for diagnostic accuracy?

Answer 15

Clinical trials and cross sectionals

Question 16

The best type of study for prognosis?

Answer 16

Clinical trials (placebo arm of RCT) and cohort study

Question 17

The best type of studies to evaluate the harm ?

Answer 17

Clinical trials and cohort study and case-control.

Question 18

The best type of studies to study the etiology ?

Answer 18

Cohort studies and case control.

Question 19

Likelihood ratio (LR+):

Answer 19

Sensitivity/1-specificity
(If the result is = or > 10 that means that test post test probability is higher and most likely they had the disease)
more likely a test result is to be found in the “diseased.”

Question 20

Likelihood ratio (LR-):

Answer 20

1-Sensitivity/specificity
(if likelihood less than 0.2 that means the test role out the disease with high post-test propability)
less likely a test result is to be found in the “diseased.”

Question 21

Each Outcome has five elements:

Answer 21

1. Domain
2. Specific measurement(s)
3. Specific metric(s)
4. Method(s) of aggregation
5. Time point(s)

Question 22

Pragmatic trials are

Answer 22

designed to evaluate the effectiveness of interventions in real-life routine practice conditions, whereas explanatory trials aim to test whether an intervention works under optimal situations. Pragmatic trials produce results that can be generalized and applied in routine practice settings.

Question 23

Verification bias seen in

Answer 23

Cross sectional

Question 24

verification bias is

Answer 24

type of measurement bias in which the results of a diagnostic test affect whether the gold standard procedure is used to verify the test result.

(sometimes referred to as “work-up bias”) occurs during investigations of diagnostic test accuracy when there is a difference in testing strategy between groups of individuals, leading to differing ways of verifying the disease of interest.

Question 25

Publication bias

Answer 25

the failure to publish the results of a study “on the basis of the direction or strength of the study findings

Question 26

To calculate NNT

Answer 26

NNT (number needed to treat) = 1/ ARR

Question 27

To calculate Absolute risk reduction (ARR) – also called risk difference (RD) –

Answer 27

= ARC - ART ARC = the AR of events in the control group ART = the AR of events in the treatment group

Question 28

RR (relative risk) =

Answer 28

ART / ARC

Question 29

RRR (relative risk reduction) =

Answer 29

(ARC – ART) / ARC | RRR = 1 – RR

Question 30

AR (absolute risk) = 

Answer 30

the number of events (good or bad) in treated or control groups, divided by the number of people in that group.

Question 31

If the RR (the relative risk) or the OR (the odds ratio) = 1, or the CI (the confidence interval) cross the line of unity, what does that mean ?

Answer 31

then there is no significant difference between treatment and control groups. If the RR >1, and the CI does not include 1, events are significantly more likely in the treatment than the control group. If the RR <1, and the CI does not include 1, events are significantly less likely in the treatment than the control group.

Question 32

How to check for publication bias

Answer 32

funnel plot can be used to examine whether ESs from smaller studies show more variability than those from larger studies. (Can be checked only by logistic regression and eager ??) If there is no bias, 95% of studies should lie within the triangle a. A larger sample size increases precision so small studies will be scattered widely at the base of the triangle whereas larger studies (more powerful) will be at the top and have a narrow spread. Funnel plots should be symmetric in the absence of study heterogeneity and publication bias

Question 33

Attritional bias can be avoided by

Answer 33

Intention to treat analysis

Question 34

Referral bias or tertiary hospital bias

Answer 34

type of selection bias. People who are referred into studies are frequently different from those who are not, meaning that the results of a trial may not generalize well to the general population.

Question 35

How to solve the drop-out (loss of FU) and demographic variations in cohort study and case-control?

Answer 35

- Sub-group analysis (stratified analysis) - multiple regression analysis The only problem about this it is going to decrease the sample size

Question 36

Unacceptable Loss of follow up percentage depends on

Answer 36

Observed event rate

Question 37

Median survival curve (half-life)

Answer 37

How long it takes to 55% of population survive

Question 38

Applicability (3 Ps)

Answer 38

Paper of best available evidence Physician experience Patient’s value and homogenous group

Question 39

The  World  Health  Organisation  define the maternal  mortality  ratio  as 

Answer 39

Maternal  deaths  per  100,000  livebirths 

Question 40

if I square (inconsistency) less than 50 % that means (or p value is Insignificant)

Answer 40

Heterogeneity is Insignificant

Question 41

P value of effectiveness with drug

Answer 41

Type 1 error

Question 42

One of the disadvantages of the mean is

Answer 42

its sensitivity to extreme values.

Question 43

The p-value is

Answer 43

a probability that the observed difference is due to chance or due to sampling error.

Question 44

The α level (also referred to as type I error) is

Answer 44

it is the error taking place when making the inference, and is the probability of rejecting a true null hypothesis.

Question 45

the β (also referred to as type II error) is

Answer 45

the error when making the inference, and is the probability of accepting a false null hypothesis.

Question 46

There are 5 ways to control for confounding:

Answer 46

In design stage: ▪︎Randomization (in clinical trial) ▪︎Restriction (including subjects who are homogeneous in terms of the confounder) ▪︎Matching (in case control studies) In analysis stage: ▪︎Stratification (assessing the association separately for the levels of the confounder) ▪︎Multivariate analyses (statistical technique that removes the effect of the confounder) The most effective way to control confounding is the multivariate analyses which necessitates collecting relevant information on the potential confounder so that it can be adjusted in the analyses.

Question 47

Reporting bias or Observer Bias (Ascertainment Bias, Detection Bias, Assessment Bias) can be avoided by

Answer 47

Triple blinding

Question 48

Tertiary (referral or centripetal) bias can be avoided by

Answer 48

Multi- centres studies

Question 49

Odd ratio in case control equation

Answer 49

ad/bc

Question 50

Relative risk calculation

Answer 50

=a /a+b ÷ c/c+d

Question 51

Performance bias can be avoided by

Answer 51

- Standardisation of care protocol | - blinding of care providers and patients.

Question 52

Detection bias can be avoided by

Answer 52

Double blinded studies

Question 53

When you Compare 3 normally Distributed group which test Preferred to use

Answer 53

``` ANOVA test (Analysis of variance) ```

Question 54

if you Comparing Pre-/Post treatment result which test Prefer to us

Answer 54

T-test for paired sample

Question 55

Chi-sequare used for

Answer 55

to test relationship btw two categorical variable

Question 56

Absolute risk reduction

Answer 56

= control event rate - exposure event rate | = C/c+d - a/a +b

Question 57

Attributable risk (or excess risk/ ARI) calculation

Answer 57

= a/a +b - c/c+d

Question 58

independent (non paired or student) t-test used for

Answer 58

Continuous with categorical variables

Question 59

The probability of rejecting a false null hypothesis (B) =

Answer 59

1-B

Question 60

One sample t-test used for

Answer 60

It is a test used for assessing the difference between a continuous variable and a fixed reference value, such as the difference between the observed SBP and the normal value (of 120 as an example).

Question 61

Paired t-test:

Answer 61

It is a test used to assess the association between two continuous measurements, which are related to each other, such as heart rate before and after taking a certain medication.

Question 62

Analysis of variance (ANOVA):

Answer 62

It is a test to assess the difference between a categorical variable with more than two levels and a continuous one, such as the difference in age between patients of different severity of illness (mild, moderate, and severe).

Question 63

Correlation:

Answer 63

It is a test used to assess the association between two continuous variables, such as SBP and age.

Question 64

Correlation:

Answer 64

It is a test used to assess the association between two continuous variables, such as SBP and age.

Question 65

The value of the power desired (1-?), and it is usually considered at ?

Answer 65

The value of the power desired (1- beta), and it is usually considered at 0.8 (80%).

Question 66

Risk difference is

Answer 66

also called attributable risk and it measures the difference in the risks between the exposure groups.

Question 67

The way to avoid selection bias is by

Answer 67

employing strict inclusion/exclusion criteria, as well as applying a random selection from the target population.

Question 68

Selection bias is

Answer 68

a systematic error that occurs at the stage where improper procedures are followed when recruiting subjects into the study.

Question 69

Information bias is

Answer 69

another systematic error that occurs at the stage of data collection, where the information collected are inaccurate, and this could be at the level of the exposure, the outcome, or other factors. This could take place when imprecise measurement instruments or invalidated questionnaires are used. Another source of information bias is introduced by subjects, such as recall bias, or reluctance to tell the truth. A third source of information bias is introduced by the interviewer when he/she probes for specific answers.

Question 70

information bias is avoided by

Answer 70

using validated questionnaires as well as following a structured method to collect information.

Question 71

The most effective way to control confounding is

Answer 71

the multivariate analyses which necessitates collecting relevant information on the potential confounder so that it can be adjusted in the analyses.

Question 72

Maternal Mortality Rate :

Answer 72

maternal death/100,000 women of reproductive age (women)

Question 73

Perinatal Mortality Rate :

Answer 73

IUFD+1 st week death/1000 Total births | It is usually expressed at the rate per thousand total births over one year

Question 74

Neonatal Mortality Rate :

Answer 74

NND (28day) / 1000 Live births

Question 75

Nuremberg Code of experiment:

Answer 75

o Has voluntary, well-informed consent o experiment aim at positive results o It should be based on previous knowledge that justifies the experiment. o Avoids unnecessary harm. o Shouldn’t be done when there is risk of death or disabling injury. o The risks should not exceed the expected benefits. o Staff must be fully trained & qualified. o Subjects are free to quit the experiment at any point o Stop the experiment at any point when continuation dangerous.

Question 76

Baseline cohort (adding baseline characteristics) is like

Answer 76

Cross sectional study

Question 77

Minimal reviewers (to abstract study)/ studies to do systemic review …

Answer 77

2 reviewers | 2 studies

Question 78

Steps of an audit Cycle

Answer 78

1. Initial needs assessment 2. Identification of standards 3. Data collection 4. Recommendations 5. Re-audit

Question 79

Standard error of the mean (SEM) =

Answer 79

standard deviation divided by the square root of n.

Question 80

In 'negatively skewed' distribution locate mean, median and mode

Answer 80

'negatively skewed' where the distribution of data about the mean tails off to the left with the majority of points being greater (the median and the mode are greater than the mean).

Question 81

Tests used to compare two means

Answer 81