Albumin is a serum protein of ~69,000 Daltons, possessing a cumulative negative charge. Under normal circumstances, the size and charge of this macromolecule prevents its passage from the circulation into the renal tubules, with only small amounts being detectible in urine. However, during progressive disease, damage occurs over time, allowing albumin through the glomerulus. A finding of abnormal amounts of albumin in the urine (albuminuria) indicates the presence of renal damage.
Historically, the terms microalbumin and microalbuminuria have been used to describe urine albumin/albuminuria. Many textbooks will reference these terms, and this will still be an orderable test for many laboratories. These terms are no longer recommended for use and will not be employed in this discussion (Inker, 2014).
