Trace proteinuria detected via dipstick test is associated with kidney function decline and new-onset overt proteinuria: the Japan Specific Health Checkups (J-SHC) Study

Background Microalbuminuria is associated with mortality, cardiovascular disease, and end-stage kidney disease. The association between trace proteinuria (detected via dipstick test) and kidney outcomes is unclear. Methods This nationwide longitudinal study used data from the Japan Specific Health Checkups Study conducted during 2008–2014. The frequency of trace proteinuria (detected via dipstick test) during first two visits was used as an exposure variable (TrUP 0/2, no trace proteinuria; TrUP 1/2, detected once; TrUP 2/2, detected twice), and kidney outcomes were evaluated. The association between the frequency of trace proteinuria and incidence of 1.5-fold increase in serum creatinine levels and overt proteinuria was analyzed using Cox regression analysis. Trajectories of estimated glomerular filtration rate (eGFR) were compared using a mixed-effect model. Results Among 306,317 participants, 3188 and 17,461 developed a 1.5-fold increase in serum creatinine levels and new-onset overt proteinuria, respectively, during the median follow-up period of 36.2 months. The adjusted hazard ratio (HR) and 95% confidence interval (CI) for 1.5-fold increase in serum creatinine level in the TrUP 1/2 and TrUP 2/2 groups, compared to TrUP 0/2 group, were 1.23 (1.07–1.42) and 1.39 (1.01–1.92), respectively, and the adjusted HR (95% CI) for overt proteinuria were 2.94 (2.83–3.06) and 5.14 (4.80–5.51), respectively. The eGFR decline rates in the TrUP 1/2 and TrUP 2/2 groups were higher than that in the TrUP 0/2 group ( p for interaction < 0.001). Conclusions Trace proteinuria (detected via dipstick test) was associated with subsequent kidney function decline and overt proteinuria in the general population.