Citation

Are the results of this diagnostic study valid?

1. Were there clearly defined groups of patients, similar in all important ways other than exposure to the treatment or other cause?
   
2. Were treatments/exposures and clinical outcomes measured in the same ways in both groups (was the assessment of outcomes either objective or blinded to exposure)?
   
3. Was the follow-up of study patients complete and long enough?
   

Is it clear that the exposure preceded the onset of the outcome?

1. Is there a dose-response gradient?
   
2. Is there positive evidence from a "dechallenge-rechallenge" study?
   
3. Is the association consistent from study to study?
   
4. Does the association make biological sense?
   

Are the valid results of this diagnostic study important?

In a randomised trial or cohort study: relative risk = RR = {a/(a+b)}/{c/(c+d)}
In a case-control study: odds ratio (or relative odds) = OR = ad/bc

Should these valid, potentially important results change the treatment of your patient?

1. Is your patient so different from those in the study that its results don't apply?
   
2. What are your patient's risks of the adverse event?
   
   To calculate the NNH (number of patients you need to treat to harm one of them) for any odds ratio (OR) and your patient's expected event rate for this adverse event if they were not exposed to this treatment (PEER):
   
   
3. What are your patient's preferences, concerns and expectations from this treatment?
   
4. What alternative treatments are available?
   

Additional Notes