How much of a role Lp-PLA2 plays in inducing artery damage is hotly debated.

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Diadexus inherited from SmithKline the new heart risk factor, called Lp-PLA2, or lipoprotein-associated phospholipase A2.

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GlaxoSmithkline researchers discovered the gene for Lp-PLA2 a decade ago with the help of a gene database licensed from Human Genome Sciences.

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Over five years those with high Lp-PLA2 levels suffered heart attacks or required heart procedures twice as often as those with low levels.

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If true, Diadexus' Lp-PLA2 test could identify healthy men who are at risk of heart problems, letting them improve their diets and take other preventive steps.

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It is testing compounds that block an enzyme, called Lp-PLA2, that attaches to cholesterol particles and chops off globs of fat that attract immune cells into the arteries.

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But a more recent study of 12, 000 American men and women found that high Lp-PLA2 levels were an independent heart-disease risk factor mainly in those patients with relatively low cholesterol levels.

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In one study of 1, 740 men with high cholesterol, Scottish researchers found that men with high levels of the Lp-PLA2 enzyme had twice the risk of heart attacks, an effect that was statistically independent of their cholesterol levels.

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