Measuring Albuminuria in Individuals With Obesity: Pitfalls of the Urinary Albumin-Creatinine Ratio

An increased urinary albumin excretion rate is an important early risk factor for CKD and other major outcomes and is usually measured using the urinary albumin-to-creatinine ratio (ACR). Obesity is highly prevalent in the general and CKD populations and an independent risk factor for moderately increased albuminuria (henceforth, moderate albuminuria). In this review we describe how the ACR was developed and used to define moderate albuminuria. We then investigate how bias related to urinary creatinine excretion is introduced into the ACR measurement and how the use of the 30 mg/g threshold decreases the performance of the test in populations with higher muscle mass, with a primary focus on why and how this occurs in the obese population. The discussion then raises several strategies that can be used to mitigate such bias. This review provides a comprehensive overview of the medical literature on the uses and limitations of ACR in individuals with obesity and critically assesses related issues. It also raises into question the widely accepted 30 mg/g threshold as universally adequate for the diagnosis of moderate albuminuria. The implications of our review are relevant for clinicians, epidemiologists and clinical trialists.