Validation of Surrogate Outcomes: Application to Biomarkers of Atherosclerosis

Abstract

Statement of the problem: Many methods for surrogate outcome validation require individual patient data which is often inaccessible by clinical trialists. Methods: A review was performed to identify statistical methods for surrogate outcome validation that may be implemented using summary data from published clinical trials. The methods were used to evaluate carotid intima-media thickness (CIMT) as a surrogate outcome for cardiovascular events in a systematic review of randomized trials of interventions for atherosclerosis. Results: the review of methods identified five procedures. At two or more years of follow-up, there was a marginally significant association of CIMT with myocardial infarction and a statistically significant association with cardiovascular mortality. At ≥ four years of follow-up, a statistically significant, negative relationship was observed between CIMT and stroke. Conclusions: CIMT may be a valid surrogate outcome for myocardial infarction and cardiovascular mortality. Additional data is needed to evaluate CIMT in specific drug classes.