One person in five carries a blood fat nobody measures

It is called lipoprotein(a) and resembles LDL cholesterol, the kind usually described as bad, with the addition of a protein that changes how it behaves in the arteries. Roughly one person in five has elevated levels, almost always without knowing it, because it causes no symptoms and because the measurement is not among the blood tests ordered as a matter of routine.

An analysis presented at the scientific sessions of the Society for Cardiovascular Angiography and Interventions and at the Canadian interventional cardiology summit in Montreal revisited data from 20,070 participants over the age of forty drawn from three clinical trials funded by the American national health institutes: Accord, Peace and Sprint. These were studies designed for other purposes, which means the participants were already monitored, already treated and already undergoing regular checks.

In patients with very high lipoprotein(a), at or above 175 nanomoles per litre, the risk of major cardiovascular events was 31 per cent higher, the risk of cardiovascular death 49 per cent higher and the risk of stroke 64 per cent higher. The relevant point is that these increases appear in people already receiving standard therapy: the risk tied to lipoprotein(a) is not erased by treating LDL cholesterol and blood pressure.

Why nobody looks for it

The reason is partly historical. Lipoprotein(a) levels are determined almost entirely by genetics, stay stable for life and do not shift with diet, physical activity or statins. For decades it therefore remained a value that could not be used to change treatment, and preventive medicine tends not to look for what it cannot act on. Two things have changed in the meantime: the arrival of experimental drugs aimed at lipoprotein(a), now in advanced trials, and the recognition that knowing the value at least allows a more aggressive approach to every other risk factor.

That is the direction of the recommendation from Subhash Banerjee, of Baylor Scott and White in Dallas, one of the authors of the analysis: have lipoprotein(a) measured and, if the value is high, work with your doctor to lower LDL cholesterol and control the other factors more firmly than usual. Since the value does not change, a single test in a lifetime would be enough. The test costs little; the obstacle is that almost nobody orders it.