Critical Appraisal Of Lit Flashcards
Rct
Double blinded?
Was allocation treatment groups concealed from those responsible for recruiting the subjects?
We’re all randomised participants included in the analysis?
Cohort studies
How were the subjects selected for the new intervention?
How were the subjected selected for the comparison or control group?
Does the study adequately control for demographic characteristics, clinical features and other potential confounding variables in the design or analysis?
Was the measure of outcomes unbias? Or blinded to treatment group ajdncomparable across groups?
Was follow up long enough for outcomes to occur?
Was follow up complete and were there exclusions from the analysis?
Case control studies
How were cases defined and selected?
How were controls defined and selected?
Does the study adequately control for demographic characteristics, clinical features and other potenital confounding variables in the design or analysis?
Was the measurement of exposure to factor of interest eg the new intervention, adequate and kept blinded to the case/ control status?
We’re all selected subjects included in the analysis?
Systemic reviews
Was an adequate search strategy used?
We’re the inclusion criteria appropriate and applied in an unbiased way
Was a quality assessment included studies undertaken?
We’re the characteristics and results of the individuals studies appropriately summarised?
We’re the methods for pooling data appropriate?
We’re sources of heterogeneity explored?
Validity
Internal- was the research done right?
Potential biases and their influence on results
Quality assessment of individual studies
Participants representative of the study
Need to use relevant inclusion/ exclusion criteria
Need a large enough samples
Calculation needs to be done to determine this size
External- does the same thing happen in other settings
Publication bias
Investigators and journals publish positive results from small studies more frequently than negative results from similar sized studies
Selection bias
Was assignment to treatment really randomised? How was this achieved?
We’re the groups similar at the start of the trial?
Follow up:
We’re all patients who entered the trial properly accounted for at the end? This is called intention to treat.
Was follow up complete >80%?
Was loss to follow up similar in control and intervention groups?
After drop out, which results were included eg last recorded, or entry levels
Measurement bias
We’re patients, health workers and study personnel blinded to treatment? Could they have become aware of treatment allocation?
Where there differences in the care provided apart from the intervention being evaluated?
We’re there differences in outcome assessment?
Was measurement of exposure inaccurate?
Was measurement of the outcome different in those who were exposed to those who were not?
Was measurement of outcome inaccurate?
In case control studies was the there recall or observer bias?
How was the disease diagnosis made? Was it diagnosed accurately in case control studies?
Reader bias
Failure to accept a study outcome because it disagreed with threat previously held view or
Accept a poor quality study as true because it agrees with their view.
Be open minded and don’t be gullible
Are the results important?
Size of the effect
How the intervention or treatment compares with doing nothing and whether the effect is clinically important
As the distance of the study estimate from the null value increases and if only clinically important effects are included in the confidence interval, the size of the effect increases
Relates to the size of the measure (point estimate or treatment effect and the values included in the corresponding 95% CI)
Measures of treatment each differ eg continuous scale and dichotomous or binary scale (improved/ not improved, hospital readmission, achieving full remission) l
Relative risk RR
Risk of an outcome in the treatment group divided by risk of outcome in control group
RR tells us how many times more likely it is that an event will occur in the treatment group relative to the control group
RR=1 means that there is no difference between the two groups
RR<1 means treatment reduced risk of outcome
RE>1 means treatment increased risk of outcome
Absolute risk reduction
Risk of outcomes in the control group minus risk of outcome in the treatment group (absolute risk differences)
ARR tells us the absolute difference in the rates of events between the two groups and it gives an indication of the baseline risk and treatment effect
ARR= 0 means there is no difference between the two groups
Relative risk reduction RRR
ARR divided by the risk of outcome in the control group
RRR tells us the reduction in the rate of outcome in the treatment group relative to the control group
Numbers needed to treat NNT
1/ARR
NNT tells us the number of patients we need to treat with the treatment under consideration in order to prevent 1 bad outcome
