If reducing proteinuria improves cardiovascular outcomes, urine dipstick testing will become crucial in hypertension

It has been known for many years that patients with chronic kidney disease have a significantly increased risk of cardiovascular morbidity and mortality. Many studies have shown that, in renal failure, increasing proteinuria and worse renal function are associated with more rapid progression and a higher incidence of cardiovascular events. Does the same hold true for patients with relatively minor degrees of renal impairment and low levels of proteinuria, even microalbuminuria? Is the combination especially important? And does this affect the management of patients?

First some technicalities. Proteinuria usually refers to protein that is detectable in urine with conventional urine dipsticks, and the amount of protein can vary from 300 mg to several grams a day. Proteinuria can be quantified reliably and easily by using spot urine protein: creatinine ratios, where normal is said to be < 20 mg/mmol (but see below). Just to confuse the issue, diabetologists have for many years measured albumin (rather than total protein) excretion in urine as an excretion rate (mg/day or μg/minute) and more recently as albumin: creatinine ratios. In patients with low levels of proteinuria the two results may be quite different since much of the urinary protein …