surrogate endpoint | The Ethical Nag

I like how the veteran health journalist Andrew Holtz once explained the interesting concept of surrogate or intermediate endpoints for us dull-witted patients. He cites, for example, studies on patients with diabetes that included aggressive control of blood sugar, high blood pressure and cholesterol in people considered to be at very high risk for heart attacks. But oddly enough, this research showed that:

strict management of blood sugar did not reduce heart attack deaths
reduction in high blood pressure levels did not reduce heart attack deaths
controlling high LDL cholesterol numbers with the use of statin drugs did not reduce heart attack deaths

Holtz explains that lab results may not actually be accurate predictors of mortality – they are merely intermediate or surrogate endpoints along the way.

And just because a drug improves lab test results doesn’t mean it saves lives – despite the efforts of Big Pharma to convince drug prescribers otherwise. Continue reading →

In the wonderful world of modern medicine, there are pesky little exceptions to every rule. For example, cardiologists tell us that people with high LDL (bad) cholesterol numbers are more at risk for heart attack. Yet we know that not everybody with dangerously high cholesterol levels suffers a heart attack, and not all heart attack patients have high cholesterol. In France, cardiologists puzzle over the “French Paradox” in which French citizens who eat more high-fat dairy foods, smoke more, and exercise less than all of their European neighbours have one of the lowest rates of heart disease in Europe.

This is what statisticians call intermediate or surrogate endpoints. It means you can’t really predict the final consequences based on how things are going along the way.

Consider the 2010 World Cup in South Africa for a similar illustration of intermediate endpoints. Sports pundits, for example, insist that, generally speaking, the team that can maintain possession of the soccer ball for most of the match will be the team that ultimately wins. Makes sense, doesn’t it? However, ball possession alone may not actually mean much at all to the end result. Here’s why: Continue reading →