Proteinuria is a determinant of quality of life in diabetic nephropathy: modeling lagged effects with path analysis.

BACKGROUND Diabetic nephropathy with overt proteinuria often progresses relentlessly to end-stage renal disease (ESRD). MATERIAL AND METHODS To answer the question whether it is impaired glomerular filtration rate (GFR) or its precursor proteinuria which is more related with multiple domains of health-related quality of life (HRQOL), we measured GFR and proteinuria in 44 patients with type 2 diabetes and overt nephropathy and repeated the measurements after 4 months. 38 patients with ESRD due to diabetic nephropathy served as a control group. We used path analysis to examine the association of baseline proteinuria and GFR with baseline and subsequent HRQOL scales. RESULTS Compared to patients with ESRD, patients with non-dialysis CKD had Kidney Disease Burden (KDB) that was, on a scale from 0 to 100, 19.8 better (95% CI 6.9-32.8) (p = 0.003). Mental component score (MCS) did not differ and physical component score (PCS) was worse in non-dialysis CKD patients by 8.5 (p < 0.001). Proteinuria at baseline was a predictor of PCS, MCS and KDB score at 4 months, suggesting a lagged effect of proteinuria on HRQOL after controlling for the autoregressive effects. GFR was not shown to have a significant impact on HRQOL. One log unit increase in proteinuria was associated with 3.8 (p = 0.011) fall in PCS, 3.3 (p = 0.043) fall in MCS and 10.6 (p = 0.006) fall in KDB. CONCLUSION In patients with advanced diabetic nephropathy, we found that proteinuria has a lagged and profound effect on multiple domains of HRQOL.