Paper Critique

Question 1

Under what five headings should you critique a paper?

Answer 1

Clinical relevance
Study design
Flow chart of study design
Validity of methods
Results and performance data
Conclusion - significant findings and implications of study

Question 2

What should by included in your statement of clinical relevance?

Answer 2

Prevalence/incidence/any worrying trends etc
Morbidity/mortality
Virulence or resistance of pathogen
Outbreak - impact in hospital/community, policy, ,education
Validation of a new method - improved TAT, performance indicators etc

What is currently known
What is unknown and what needs to be done
How this study addresses the question/Study Aim

Question 3

What should you include in your statement on study design?

Answer 3

Patient population - type, number
Sample type and number
Specimen detail if relevant
Proposed methods of investigation
Limited method detail

Question 4

What should you include in your flow chart

Answer 4

Need specimen numbers at each step

Include methods of investigating discordant results

Question 5

What should you include in validity of methods?

Answer 5

Assay strategy
What is the reference/gold standard
Use of suitable methods
Use of suitable and suffienient controls
Result definitions - true positives and true negatives
Resolution of discordant results

Question 6

What are the four different assay strategies?

Answer 6

Comparative
New assay design
Validation of a new method
Clinical trial

Question 7

What should you include in your summary

Answer 7

Summarise the epidemiology results: prevalence, incidence and trends

Summarise the performance data/test validity: p-value, sensitivity, specificity, postive/negative predictive value

Question 8

What is prevalence?

Answer 8

Prevalence looks at all existing cases that have an infection over a speicified period of time

It includes all cases, both new and pre-existing, in the population at the specified time

number of affected/total number x 100 = % prevalence

Question 9

What is prevalence?

Answer 9

Prevalence looks at all existing cases that have an infection over a speicified period of time

It includes all cases, both new and pre-existing, in the population at the specified time

number of affected/total number x 100 = % prevalence

Question 10

What is point prevalence?

Answer 10

The number of cases of health events at a certain time

Question 11

What is incidence

Answer 11

Incidence looks at new cases - those that develop infection over a period of time

Incidence proportion, incidence rate, crude incidence rate

Question 12

What is incidence proportion, how is it calculated?

Answer 12

What happens over an accumulation of time

(Number of new cases of infection during specified period x 100)/(size of at risk population of start of period)

i.e. new infections x 100/total number of patients

Question 13

What is incidence rate and how is it calculated?

Answer 13

What is happening moment to moment or year to year

Number of new cases of infection during specified period/ime each person was observed, totalled for all persons

Question 14

What is crude incidence rate and how is it calculated?

Answer 14

new infections/specific year x 100,000

(Number of cases of infetion during specified year x 100,000)/size of at risk population

Question 15

What is test validity?

Answer 15

The ability of a test to accurately identify infected pathogen and non-infected individuals

It can only be determined if tet accuracy compares to the gold stadard or reference method i.e. establishes true infection status

Question 16

What are two key features of an ideal screening test?

Answer 16

Exquisitely sensitive - high probability of detecting infection

Extremely specific - high probability no infection will test negative

Question 17

What are three features of a reference method normally?

Answer 17

Very accurate, but more expensive diagnostic test

Final diagnosis based on a series of diagnostic tests

Best available method currently in practice

Question 18

How do you test the validity of a method?

Answer 18

Use a 2x2 contingency table

Comparing reference method to new test method

True positive: positive + positive
False negative: positive reference but neg new metho
False positive: negative reference but positive new
true negative: negative + negative

Sensitivity = focus on positives - how many +/ves was the new method able to detect
Specificity = fous on negatives - how many -/ves was the new method able to detect

Question 19

What is sensitivity and how do you calculate it?

Answer 19

Probability of a test correctly identifying patient with infection

Sensitivity = true positives

(true positives x 100)/ true positives + false negatives

Question 20

What is specificity and how is it calculated?

Answer 20

Probability of a test correctly identifying patients with no infection i.e true negatives

Specificity = true negatives x 100/ true negatives + false positives

Question 21

What is positive predictive value, how is it calculated

Answer 21

Probability (proportion) of people with a positive test who truly have the infection

True positives x 100/ true positives + false positives

e.g. if a patient gets a posiive screen how worried should they be that they have the infection

Question 22

What is negative predictive value. how is it calculated?

Answer 22

Probability (proportion) of people with a negative test who truly hav no infectionn

True negatives x 100/ true negatives + false negatives

e.g. if a patient gets a negative screen test -how relieved should they be

Question 23

What should you include in your conclusion

Answer 23

Is the discussion/conclusion substantiated
Is the statement on relative performance of assay supported by findings in the study
How do the findings compare to the results of other studies
Have the limitations of the study been acknowledged
Are the implications/application of study findings feasible

Question 24

What are the four objectives of a study design

Answer 24

Construct a brief project proposal outlining the clinical background and focus of the proposed study

Outline the aims of the proposed study

Construct a flowchart detailing the proposed study design

explain the reasoning to support the key elements of the study design