Intermediaire uitkomstmaten in medisch onderzoek

Conflict of interest: none declared. Financial support: none declared.

• An intermediate variable such as blood pressure is part of the causal pathway of mechanisms to a clinical outcome, e.g. myocardial infarction. An intervention affects a clinical outcome through its effect on that intermediate variable.

• In studies designed to assess the effects of interventions an intermediate variable may be used as surrogate for clinical outcomes. Such an endpoint is also known as an intermediate endpoint.

• Intervention studies with intermediate endpoints are commonly performed in medical research to evaluate the effects of an intervention on clinical outcomes.

• Intervention studies with an intermediate endpoint are conducted in a smaller study population and with a shorter duration of follow-up than studies using clinical outcomes.

• An intermediate variable is not eligible as an intermediate endpoint when the intervention also affects other biological mechanisms that subsequently affect the clinical endpoint.

• Due to a smaller sample size and shorter study duration, side effects of intervention are more difficult to evaluate in studies with an intermediate endpoint than in studies with clinical endpoints.