The urine albumin/creatinine ratio (UACR) is a diagnostic test that measures the amount of albumin (a protein) relative to creatinine in urine, providing a more accurate assessment of kidney function than a simple urine dipstick. It is clinically significant for detecting early stages of kidney damage, particularly in patients with diabetes or hypertension. An elevated UACR indicates increased risk of cardiovascular disease and progression to chronic kidney disease.