Urine albumin-to-creatinine ratio (UACR)

The urine albumin-to-creatinine ratio (UACR) quantifies albumin leaking into urine relative to urinary creatinine, correcting for hydration status. A healthy glomerular filtration barrier retains virtually all albumin; persistent UACR ≥ 30 mg/g signals structural or functional breach of the glomerular basement membrane or endothelium, while values ≥ 300 mg/g define overt macroalbuminuria. Together with estimated GFR (eGFR), UACR forms one of the two pillars of the KDIGO 2024 CGA (Cause, GFR, Albuminuria) classification for chronic kidney disease staging and risk stratification. Beyond kidney health, UACR reflects systemic endothelial dysfunction: albumin escaping glomerular capillaries mirrors generalised vascular permeability, predicting cardiovascular events independently of traditional risk factors. In the PREVEND cohort (Hillege et al. 2002, n ≈ 40,500 general-population adults, Groningen), even sub-clinical albuminuria below 30 mg/g showed a continuous, graded association with all-cause and cardiovascular mortality, independent of blood pressure, diabetes status, and kidney function. A 2023 KNHANES-based study by Kim et al. (n = 19,340 Korean adults) confirmed that UACR above 30 mg/g is associated with elevated cardiovascular risk across diabetic and non-diabetic subgroups. Screening requires only a single first-morning or random mid-stream urine sample, but two or more elevated readings at least three months apart are needed to distinguish persistent from transient albuminuria.