In a non-diabetic Japanese population, the combination of macroalbuminuria and increased urine beta 2-microglobulin predicts a decline of renal function: The Takahata study

Background. Glomerular and tubular damage are important factors in the development of renal insufficiency. However, the interaction of these factors is largely unknown in the non-diabetic Japanese population. To clarify the relationship between renal insufficiency and both glomerular and tubular damage, we conducted a community-based study using albuminuria and urine beta 2-microglobulin as markers of glomerular and tubular damages, respecti- vely. Methods. Subjects of this study were 2816 non-diabetic individuals >40 years old in Takahata, Japan. The urine albumin-creatinine ratio (UACR) and urine beta 2-microglobulin-creatinine ratio (UBCR) were assessed from single spot urine. The glomerular filtration rate (eGFR) was estimated using the abbreviated MDRD equation with a Japanese coefficient. Results. The prevalence of albuminuria (UACR >20 mg/ g in men and >30 mg/g in women), increased UBCR (>300 μg/g) and renal insufficiency (eGFR <60 mL/ min/1.73 m²) were 21.0%, 12.5% and 21.7%, respectively, and there was only a small overlap between the three. The mean eGFR was significantly lower in subjects with macroalbuminuria (UACR >200 mg/g in men and >300 mg/g in women) and increased UBCR. No urinary abnormalities were observed in 71.7% of the 611 subjects with renal insufficiency, and were more common in young, women and the non-hypertensive population. The 1-year decline of eGFR was greatest in subjects with an overlap of macroalbuminuria and increased UBCR. Conclusions. This study indicated that only a small part of renal insufficiency accompanied increased urine albumin or beta 2-microglobulin in the non-diabetic Japanese population. The combination of macroalbuminuria and increased urine beta 2-microglobulin might predict faster renal deterioration.