Индекс альбумин/креатинин\ACR, Albumin\Creatinine Ratio

Urine Albumin-to-Creatinine Ratio (ACR, UACR) is used to identify albuminuria early and to gauge prognosis in chronic kidney disease, including diabetic kidney disease. The test supports longitudinal assessment of kidney damage and complements risk stratification for atherosclerosis and cardiovascular events among individuals with CKD. Because it reports the albumin/creatinine ratio from a spot urine sample, UACR offers a practical alternative to 24‑hour collections and is widely applied for screening, staging, and monitoring persistent albuminuria.

Urinary albumin excretion is a sensitive marker of glomerular injury and informs diagnosis, prognosis, and treatment monitoring in kidney disease, including diabetic nephropathy. In healthy individuals, total urinary protein excretion does not exceed 150 mg/day, with albumin typically no more than 2–30 mg/day. Albuminuria above 30 mg/day suggests kidney disease and is associated with higher risk of atherosclerosis and cardiovascular events. Persistent albumin excretion of 30–300 mg/day represents an early sign of renal tissue injury. Measuring the albumin/creatinine ratio (ACR) in a spot urine sample closely agrees with 24‑hour urinary albumin measurements and is recommended as the primary screening approach because of its practicality; many laboratories report only the calculated ratio without separate albumin or creatinine values. ACR may be expressed as mg of albumin per g creatinine or per mmol creatinine. An ACR <30 mg/g corresponds to <30 mg/day and indicates normoalbuminuria; 30–300 mg/g corresponds to 30–300 mg/day (microalbuminuria); and >300 mg/g indicates >300 mg/day (macroalbuminuria). A complementary categorization uses: optimal (<10 mg/g), high‑normal (10–29 mg/g), high (30–299 mg/g), very high (300–1999 mg/g), and nephrotic (>2000 mg/g). The diagnosis of microalbuminuria requires persistence—elevations on 2 of 3 urine tests over 3–6 months—after excluding transient or orthostatic proteinuria (eg, due to fever, recent infection, or strenuous exercise). Serial ACR testing is therefore recommended for confirmation and for tracking disease course. Interpretation must consider that ACR uses urinary creatinine to account for urine concentration. Creatinine output varies with muscle mass and is influenced by sex, age, and possibly race. At the same albumin concentration, women tend to have higher ACR than men because of lower muscle mass and lower urine creatinine. Sex‑specific thresholds are often applied: microalbuminuria in women at >3.5 mg/mmol (>31 mg/g) and in men at >2.5 mg/mmol (22 mg/g). Reduced muscle mass in older adults may increase the apparent prevalence of microalbuminuria; in patients with very low or very high muscle mass, a confirmatory 24‑hour urine collection can improve accuracy. Dietary intake of meat (containing creatinine/creatine) can affect urinary creatinine and the calculated ratio. Circadian variation also matters: albumin excretion is lower overnight, so first‑morning ACR values are generally lower and yield fewer false positives than random daytime samples. An elevated daytime ACR should be confirmed with a first‑morning specimen.