Confounder/effect-modifier criteria for assessment of published chronic obstructive pulmonary disease (COPD) outcomes and markers
| Brief description of variable |
| Has methodology been standardised? |
| Has the frequency distribution been establishedIn the general population?In COPD patients? |
| Is the variable reproducible? |
| Has the influence on the treatment been established? |
| Can the measure be performed during exacerbations of COPD? |
| Is the variable influencing common comorbidities, e.g. ischaemic heart disease, diabetes mellitus or psychiatric disturbances? |
| Can the variable be used in multicentre trials? |
| In order to measure the variable, what is needed?A questionnaireEquipmentTimeTraining |
| How much does the measurement of the variable cost?CheapModerateExpensive |
| Are there any safety issues? |
| Are there any ethical issues? |
A confounder can be defined as a variable that can cause or prevent the outcome of interest, is not an intermediate variable and is associated with the factor under investigation. An effect modifier can be defined as a factor that modifies the effect of a putative causal factor under study.