3 It would be appropriate if the authors refrain from simply calling a

study 'prospective' or 'retrospective' because these terms are ill

defined. We recommend that, whenever authors use these words, they

define what they mean. Most importantly, we recommend that authors

describe exactly how and when data collection took place.

4 Give the eligibility criteria, and the sources and methods of case

ascertainment and control selection. Give the rationale for the

choice of cases and controls.

5 A study should be large enough to obtain a point estimate with a

sufficiently narrow confidence interval to meaningfully answer a

research question. Explain how the study size was arrived at.

6 Explain how matching of cases and controls was addressed

7 Describe all statistical methods, including those used to control for

confounding variables.

8 How confounding variables within the two groups controlled?

9 Discuss both direction and magnitude of any potential bias

10 Give a cautious overall interpretation of results considering

objectives, limitations, multiplicity of analyses, results from

similar studies,and other relevant evidence.

11 Discuss the generalisability (external validity) of the study results

12 The conclusion must be according to the objective.