356: Examination of prepregnancy and pregnancy urinary protein levels in healthy nulligravidas

Abstract

The diagnostic threshold for abnormal proteinuria in pregnancy is 300mg/24 hours. This threshold has been questioned. We sought to characterize 24 hour urinary profiles in healthy nulligravid women prior to and during pregnancy, identify their association with clinical preeclampsia, and compare inpatient versus outpatient urinary collection results. 102 healthy nulligravid women were recruited as part of 2 prospective clinical studies characterizing the association of prepregnancy and late pregnancy maternal physiology. 24 hour urine collections were completed at recruitment (follicular phase) and 30-32 weeks gestation in both studies but urinary collections were outpatient in one study and inpatient in the second. Urine protein was measured using the VITROS UPRO Slides kit (Ortho Diagnostics). Clinical outcomes were tracked. Data is expressed as mean ± s.d. T-test and Pearson’s correlation coefficient are used for statistical analysis with significance p<0.05. Mean subject age was 30.0 ± 4.6 and BMI 23.8 ± 4.6. Four subjects developed preeclampsia. The mean prepregnant 24 hour urine protein was 225 ± 132 mg with 68% of women above normal (150 mg) for nonpregnant individuals. 40 subjects completed third trimester urinary collection (20 inpatient and 20 outpatient) with 24 hour urine protein levels of 294 ± 196 mg. 39% of women had >300mg proteinuria, only one of which developed preeclampsia. Proteinuria was significantly greater in inpatient vs outpatient collections (395.8 ± 219.4 mg vs 197.4 ± 92.4 mg; p=0.0006). This difference was largely accounted for by volume differences (3274.7 ± 1379.2 mls vs 2625.1 ± 990.5 mls, inpatient vs outpatient); r2 =0.9. Levels of proteinuria in young women routinely exceed established thresholds for both nonpregnant and pregnant subjects and outpatient 24 hour urine collections may underestimate proteinuria in pregnancy. The current threshold for 24 hour urine protein in the diagnosis of preeclampsia may need reevaluation.