Checklist of the key points in study

Study purpose

• The aim of the study should be clearly stated.

Sample

• The sample should accurately reflect the population from which it is drawn.
• The source of the sample should be stated.
• The sampling method should be described and the sample size should be justified.
• Entry criteria and exclusions should be stated and justified.
• The number of patients lost to follow up should be stated and explanations given.

Control group

• The control group should be easily identifiable.
• The source of the controls should be explained—are they from the same population as the sample?
• Are the controls matched or randomised—to minimise bias and confounding.

Quality of measurements and outcomes

• Validity—are the measurements used regarded as valid by other investigators?
• Reproducibility—can the results be repeated or is there a reason to suspect they may be a “one off”? Blinded—were the investigators or subjects aware of their subject/control allocation?
• Quality control—has the methodology been rigorously adhered to?

Completeness

• Compliance—did all patients comply with the study?
• Drop outs—how many failed to complete the study?
• Deaths
• Missing data—how much are unavailable and why?

Distorting influences

• Extraneous treatments—other interventions that may have affected some but not all of the subjects.
• Confounding factors—Are there other variables that might influence the results?
• Appropriate analysis—Have appropriate statistical tests been used?

Validity

• All studies should be internally valid. That is, the conclusions can be logically drawn from the results produced by an appropriatemethodology.Forastudytoberegardedasvalid it must be shown that it has indeed demonstrated what it says it has. A study that is not internally valid should not be published because the findings cannot be accepted.
• The question of external validity relates to the value of the results of the study to other populations—that is, the generalisability of the results. For example, a study showing that 80% of the Swedish population has blond hair, might be used to make a sensible prediction of the incidence of blond hair in other Scandinavian countries, but would be invalid if applied to most other populations.

 

  ref.  Emerg Med J 2003;20:54-60