Surrogate markers

Surrogate markers or endpoints are those which evaluate the effect of a treatment in the hope that they represent a meaningful clinical endpoint. What matters is whether a treatment for varicose veins has alleviated the presenting symptoms and not whether sites of reflux have been obliterated or the venous filling index has improved. Clinical endpoints can be assessed using a patient reported outcome measure (PROM) like improvements in a disease specific quality of life (QoL) score or a symptom severity score. However, there are many factors which may alter a patient’s perception of their disease which may have impact on their QoL. For example, if patients’ expectations are exceeded they will have a much greater improvement in QoL. Similarly, improvements in personal circumstance and recovery from depression are likely to change a QoL score, irrespective of the success of a treatment at abolishing reflux. On some occasions a varicose vein treatment may fail to cause saphenous obliteration but the patient is very happy at the initial cosmetic result. Since reflux is the endovenous target of treatment its abolition should remain an important surrogate marker.