Trace Proteinuria and the Incidence of Overt Proteinuria After Five Years: Results of the Kanagawa Investigation of the Total Checkup Data From the National Database-5 (KITCHEN-5)

Background

Trace proteinuria (TrP), which is usually defined as ± by dipstick urinalysis, is considered as normal and of limited clinical significance. However, the relationship between TrP and overt proteinuria (OP) (≥ +1) in the future is unknown. Therefore, we investigated the association between TrP and future incidence of OP in a community-based cohort study.

Methods

TrP detected during the initial 2 years, which was classified into transient TrP (once/2 years) (T-TrP) and recurrent TrP (twice/2 years) (R-TrP); and the incidence of OP after 5 years were investigated in 292,257 general Japanese people aged 40 - 68 years who attended checkups. To determine TrP and OP, dipstick urinalysis was conducted with visual reading (VR) by medical staff or automated reading (AR) using a machine reader.

Results

Overall, T-TrP and R-TrP were observed in 24,782 (8.5%) and 3,767 (1.3%) subjects, respectively. Both types of TrP were prevalent in the detection with AR than VR. The prevalences of T-TrP and R-TrP showed J-shaped relationships against baseline body mass index (BMI), regardless of sex and BMI categories. The incident of OP after 5 years was larger (around 10%) in R-TrP than T-TrP (around 5%): approximately two times. Logistic regression analysis showed that T-TrP and R-TrP were significantly associated with OP, even after adjustment for relevant confounding factors including age, sex, and BMI (odds ratios (95% confidence intervals (CIs)): 2.77 (2.60 - 2.95) and 4.85 (4.34 - 5.43)), which were not largely altered when sub-analysis was conducted according to men and women, non-obesity and obesity, or AR and VR. In all analysis above, the odds ratios (95% CIs) of R-TrP for OP were higher than T-TrP.

Conclusions

Our findings suggest that TrP, particularly R-TrP, is substantially associated with the future incidence of OP, which may be independent of confounding factors and the methods detecting TrP.

Therapeutic management of diabetic kidney disease

During the past 10 years, a global pandemic of end-stage renal disease (ESRD) attributed to diabetes mellitus has changed the therapeutic strategies based on landmark trials that have shown that diabetic micro- and macrovascular complications might be preventable. However, the remaining risk of the progression of diabetic kidney disease to ESRD is still high, despite newly introduced anti-diabetic, antihypertensive and dyslipidemic drugs in the 21st century. Here, we show the importance of targeting remission and regression of microalbuminuria in type 2 diabetic patients. To achieve the remission and regression of microalbuminuria, physicians have revised the management strategy of diabetic patients and have to act immediately. Early detection of microalbuminuria with continuous screening, the use of renin-angiotensin system blockades, and targets for HbA1c of <7.35% and systolic blood pressure of <130 mmHg are closely associated with the remission and regression of microalbuminuria, resulting in protection against the progression of diabetic kidney disease, as well as cardiovascular events. Our concept of the natural history of diabetic kidney disease has to be modified by our results and others. Reducing microalbuminuria is therefore considered to be an important therapeutic target and could be a pivotal biomarker of therapeutic success in diabetic patients. (J Diabetes Invest, doi:10.1111/j.2040-1124.2011.00112.x, 2011).