Estimating the glomerular filtration rate and tubular dysfunction in an elderly population with normoalbuminuria in China

The prevalence and clinical risk factors of normoalbuminuric renal impairment have not yet been investigated in elderly Chinese populations. To clarify this, we conducted survey research on an elderly Chinese community population. A total of 691 elderly community participants were included in this study. Normoalbuminuria was defined as a urinary albumin to creatinine ratio (ACR) <30 mg/g in morning urine. The estimated glomerular filtration rate (eGFR) and urinary alpha-1-microglobulin to creatinine ratio (MCR) were evaluated to assess normoalbuminuric kidney impairment in this elderly population. Among the whole cohort, 30.25% had albuminuria, 8.68% showed reduced eGFR and 49.78% had increased MCR. Normoalbuminuric subjects also showed a high prevalence of low eGFR and increased MCR (6.02% for reduced eGFR and 37.55% for increased MCR). Among the normoalbuminuric participants, the highest prevalence of increased MCR was found in the subjects with diabetes (50%), whereas the highest prevalence of low eGFR was found in women (8.11%). There was no significant difference in ln-MCR values between normoalbuminuric subjects with eGFR>60 and < 60 ml/min/1.73 m2. Age, gender, diabetes and hypertension were all independent risk factors of increased MCR. Diabetes and hypertension showed no statistical influence on decreased eGFR,whereas gender carried the highest risk for reduced eGFR. Albuminuria may have limited utility as a screening marker of renal injury, as a considerable proportion of the elderly population have renal impairment despite normoalbuminuria. Rather than focusing solely on patients with diabetes or hypertension, normoalbuminuric renal impairment should be given more attention within the overall elderly population.