Table 3.

Quality of reporting

Required items to be reported in the
Method section
Assumptions for the use of a self-controlled design (whether the setting is valid for the design implementation, with regard to major assumptions)	53 (50)
Case and control period definition (including number and duration) for case-crossover studies	50/53 (94)
Risk and control period definition (including number and duration) for self-controlled case-series	49/55 (89)
Sensitivity analyses conducted (varying periods duration)	54 (50)
Statistical model	99 (93)
With the appropriate model a	99/99 (100)
Effect estimator	107 (100)
Sample size or power calculation	13 (12)
Result section
Appropriate effect estimator with a measure of variability	102 (95)
Person-time in the different periods (for self-controlled case series)	18/55 (33)
Estimate displayed
Unadjusted effect estimators	36 (34)
Adjusted effect estimators	38 (36)
Both unadjusted and adjusted effect estimators	33 (31)

Data are reported as n (%)

^aConditional logistic regression or conditional Poisson regression model for case-crossover studies, conditional Poisson regression model, Cox’s stratified proportional hazards model or conditional logistic regression model for self-controlled case series