Table 2

Methodological quality criteria

External validity
 Were the subjects asked to participate in the study representative of the entire population from which they were recruited?Yes/No/Unable to determine
Internal validity
 Were the determinants measured used accurate?Yes/No/Unable to determine
 Were the statistical tests used to assess the main outcomes appropriate?Yes/No/Unable to determine
 Were losses of patients to follow-up taken into account?Yes/No/Unable to determine
 Was there adequate adjustment for confounding in the analysis from which the main findings were drawn?Yes/No/Unable to determine