C-Reactive Protein Is a Predictor for Developing Proteinuria in a Screened Cohort

<i>Background:</i> The relationship between C-reactive protein (CRP) and proteinuria is not known. <i>Methods:</i> We examined 20,077 screenees (men: 52.4%) of the Okinawa General Health Maintenance Association (OGHMA) registry who were examined between 2004 and 2006. Cross-sectional and longitudinal relationships between CRP and dipstick proteinuria were examined. The OGHMA central laboratory measured creatinine and CRP levels using an autoanalyzer (normal: <0.30 mg/dl). The glomerular filtration rate was estimated using the Japanese formula. <i>Results:</i> The prevalence of dipstick-positive proteinuria increased from 5.2% in screenees with a low CRP level of <0.10 mg/dl to 12.3% in those with high CRP levels (0.30–0.90 mg/dl). The CRP values did not affect the mean (SD) estimated glomerular filtration rate: 76.9 (13.7) with low CRP and 76.4 (15.1) with high CRP levels. We examined the relationship between baseline CRP and the development of proteinuria among subjects screened in 2004. Of 8,315 subjects without proteinuria examined again by 2006, 370 (4.4%) had developed proteinuria. The odds ratio (95% CI) for high CRP levels (0.30–0.90 mg/dl; reference CRP: <0.10 mg/dl) was 1.433 (1.013–2.028; p = 0.0422) after adjusting for multivariate variables, suggesting that CRP is closely associated with the prevalence and incidence of proteinuria. <i>Conclusion:</i> A prospective study on the development of proteinuria among those with high CRP levels is warranted. Screenees with high CRP levels may need to be followed up carefully despite the absence of traditional risk factors for proteinuria.