Comparison between 24-h proteinuria, urinary protein/creatinine ratio and dipstick test in patients with nephropathy: Patterns of proteinuria in dipstick-negative patients

Objective. Three main tests are commonly employed for the measurement of proteinuria: the dipstick test, the urinary protein/creatinine ratio (P/C) and the 24-h urine collection. The aim of this study was to evaluate the correlation between these methods, comparing linear regression and ROC curve data. Material and methods. A total of 297 consecutive outpatients with different renal diseases were included in the study. Twenty-four-hour proteinuria was considered the reference test. Results. A high degree of correlation was observed between all the tests (p < 0.0001), the highest regression coefficient being between 24-h proteinuria and P/C (R=0.82), and the lowest between P/C and the dipstick test (R=0.72). The dipstick test failed to detect pathological proteinuria in 94 patients (31.6%). Therefore, in these subjects, the patterns of proteinuria were assessed by immunofixation and sodium dodecyl sulphate (SDS) electrophoresis. Conclusions. Our data strongly support the use of urinary P/C for the detection of proteinuria, at least in nephrology units, where the prevalence of proteinuria is likely to be high.