Microalbuminuria: do we need a new threshold?

Microalbuminuria (30–300 mg of albumin/24 h) is a well-known independent risk factor for kidney and cardiovascular disease and of mortality in diabetic, hypertensive and in the general population. However, recent studies indicate that increased risk is observed at levels of albuminuria much lower than those currently employed to define microalbuminuria. Such low levels were shown to predict heart disease and death, independent of age, sex, renal function, diabetes, hypertension and lipids, in subjects with cardiovascular disease, hypertension and in the general population; as well as to predict progression to hypertension. Correction of obesity and metabolic derangements lowered levels of albuminuria below 30 mg/24 h to levels not associated with increased risk (5–7 mg/24 h). Despite the lack of outcome studies, there is substantial evidence to indicate that the threshold for defining microalbuminuria (that is, albuminuria associated with increased risk) should be lowered by nearly three to four-fold from the currently defined threshold. It would be advisable that clinical scores and future guidelines would consider including microalbuminuria at the lower rates as an independent risk factor, and as an indication for implementing early intervention. Unfortunately, and despite the abundance of evidence, albuminuria measurements are still underutilized in clinical practice.