AimThe aim of this study was to underscore problems associated with the dipstick test and determination of protein concentration alone in spot-urine (P-test) compared with spot-urine protein-to-creatinine ratio (P/Cr test) and to determine whether urine collection for 24-h test was complete.
Material and MethodsDipstick and P/Cr tests were performed simultaneously in 357 random spot-urine specimens from 145 pregnant women, including 35 with pre-eclampsia. Positive results were defined as 1+ on dipstick test, protein concentration 30mg/dL on P-test, and P/Cr ratio0.27 (mg/mg) on P/Cr test. Sixty-four 24-h urine tests (quantification of protein in urine collected during 24h) were performed in 27 of the 145 women. We assumed that P/Cr ratio0.27 predicted significant proteinuria (urinary protein0.3g/day). The 24-h urine collection was considered incomplete when urinary creatinine excretion was<11.0mg/kg/day or >25.0mg/kg/day.
ResultsForty-four percent (69/156) of specimens with a positive test result on dipstick test contained protein<30mg/dL. Dipstick test was positive for 25.7% (69/269) of specimens with protein<30mg/dL and for 28.8% (79/274) of specimens with P/Cr ratio<0.27. P-test results were positive for 7.3% (20/274) and negative for 18.1% (15/83) of specimens with P/Cr ratio<0.27 and 0.27, respectively. Incomplete 24-h urine collection occurred in 15.6% (10/64) of 24-h urine tests. Daily urinary creatinine excretion was 702-1397mg, while creatinine concentration varied from 16mg/dL to 475mg/dL in spot-urine specimens.
ConclusionDipstick test and P-test were likely to over- and underestimate risks of significant proteinuria, respectively. The 24-h urine collection was often incomplete.