Inclusion of albuminuria in hypertension and heart guidelines

Abstract

The current recommendations by all United States guideline committees, including the American Diabetes Association and the JNC 7, include screening for microalbuminuria in those with diabetes or evidence of kidney disease, but not the general population. Internationally, both the Canadian and European Guidelines have concurred with this approach. This recommendation is due in part to the findings from long-term outcome studies that measurement of microalbuminuria, while a strong predictor of cardiovascular risk, fails to shows change in CV events if reduced. Unfortunately, this conclusion may be wrong because no randomized trial has examined the question of whether a reduction in microalbuminuria does correlate with a reduction in CV events. Thus, we don't know the answer to this question. Additionally, a recent cost-effective analysis was just published, suggesting it is not worth measuring urinary albumin because it is too expensive for the information obtained. Unfortunately, these conclusions were based on the same faulty logic that relates changes in microalbuminuria to cardiovascular events. It is clear that microalbuminuria is a cardiovascular risk factor, acknowledged by both the JNC 7 and the European Guidelines. Moreover, presence of microalbuminuria correlates strongly with elevated levels of C-reactive protein and abnormal vascular responsiveness to vasodilating stimuli. Thus, its presence indicates abnormal responses by vascular tissue, perhaps due to underlying inflammatory responses. Every clinical trial that has assessed changes in albuminuria as a secondary end point with clinical outcomes has shown a strongly positive correlation between reduction in albuminuria and greater protection of a given end organ; this effect is, in part, independent of blood pressure reduction. Thus, what is needed is a clinical trial in people at high cardiovascular risk, such as those in the INVEST or ALLHAT trials where the primary end point is change in albuminuria and its relationship to cardiovascular outcomes. Likewise, a cardiovascular primary end point could relate to the secondary end point of changes in microalbuminuria, and the latter powered appropriately to make stronger statements about albuminuria and cardiovascular outcomes. With this data, guidelines can then make much strong statements about intervention on this marker of risk.