Paper Critique Flashcards
Under what five headings should you critique a paper?
Clinical relevance
Study design
Flow chart of study design
Validity of methods
Results and performance data
Conclusion - significant findings and implications of study
What should by included in your statement of clinical relevance?
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
What should you include in your statement on study design?
Patient population - type, number
Sample type and number
Specimen detail if relevant
Proposed methods of investigation
Limited method detail
What should you include in your flow chart
Need specimen numbers at each step
Include methods of investigating discordant results
What should you include in validity of methods?
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
What are the four different assay strategies?
Comparative
New assay design
Validation of a new method
Clinical trial
What should you include in your summary
Summarise the epidemiology results: prevalence, incidence and trends
Summarise the performance data/test validity: p-value, sensitivity, specificity, postive/negative predictive value
What is prevalence?
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
What is prevalence?
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
What is point prevalence?
The number of cases of health events at a certain time
What is incidence
Incidence looks at new cases - those that develop infection over a period of time
Incidence proportion, incidence rate, crude incidence rate
What is incidence proportion, how is it calculated?
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
What is incidence rate and how is it calculated?
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
What is crude incidence rate and how is it calculated?
new infections/specific year x 100,000
(Number of cases of infetion during specified year x 100,000)/size of at risk population
What is test validity?
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
What are two key features of an ideal screening test?
Exquisitely sensitive - high probability of detecting infection
Extremely specific - high probability no infection will test negative
What are three features of a reference method normally?
Very accurate, but more expensive diagnostic test
Final diagnosis based on a series of diagnostic tests
Best available method currently in practice
How do you test the validity of a method?
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
What is sensitivity and how do you calculate it?
Probability of a test correctly identifying patient with infection
Sensitivity = true positives
(true positives x 100)/ true positives + false negatives
What is specificity and how is it calculated?
Probability of a test correctly identifying patients with no infection i.e true negatives
Specificity = true negatives x 100/ true negatives + false positives
What is positive predictive value, how is it calculated
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
What is negative predictive value. how is it calculated?
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
What should you include in your conclusion
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
What are the four objectives of a study design
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
