PROTEINURIA - INCIDENCE AND CLASSIFICATION

HOW COMMON IS IT?

Based on large observational studies, it is estimated that approximately 11.7% of the adult population in United States have abnormal urine albumin excretion.  Among the adults, the prevalence of albuminuria varies by age and presence or absence of diabetes. The prevalence is approximately 30% in adults with age 70 years: 26.6% with microalbuminuria and 3.7% with albuminuria.

At all ages, the prevalence is higher among individuals with diabetes. Among individuals with a history of diabetes, the prevalence of microalbuminuria and albuminuria is 43.2% and 8.4%, respectively, at age 70 years. Among individuals without a history of diabetes the prevalence of microalbuminuria and albuminuria is 24.2% and 3.0%, respectively, at age 70 years.

CLASSIFICATION

The severity of proteinuria is determined by the extent of protein leak which is measured by milligrams (mg) or grams (g) of protein measured during a 24-hour urine collection. This can be broadly categorized into :

• Microalbuminuria (30–150 mg)

• Mild (150–500 mg)

• Moderate (500–1000 mg)

• Heavy (1000–3000 mg)

• Nephrotic range (more than 3000 mg)


As the kidney disease progresses, more protein enters the urine. Patients with nephrotic-range proteinuria typically have extensive glomeruli damage and usually develop generalized swelling and this condition is known as nephrotic syndrome.

Proteinuria is not a disease by itself. However; it is an early and sensitive marker of kidney damage in many types of chronic kidney disease.Normal mean value for urine albumin excretion in adults is approximately 10 mg/day. Urine albumin excretion is increased by physiological variables, such as upright posture, exercise, pregnancy, and fever. Normal mean value for urine total protein is approximately 50 mg/day. Any value more than the normal may be indicative of underlying kidney disease.

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Expert Author:

Dr Roger Tan, Consultant Nephrologist