Improved methods of assessing proteinuria in hypertensive pregnancy

Abstract

Objective: To determine whether use of an automated urinalysis device will improve the accuracy of detecting proteinuria, and whether spot urine protein to creatinine ratio will provide accurate quantitation of proteinuria in hypertensive pregnant women.

Design: Prospective studies assessing the accuracy of both detection and quantitation of proteinuria.

Setting: Antenatal ward and pregnancy day assessment unit of St George Hospital, a teaching hospital in Sydney, Australia.

Population: Hypertensive pregnant women admitted to hospital or day assessment unit for management of their hypertensive disorders.

Methods: 1. Routine dipstick urinalysis and 2. urinalysis by an automated device (Clinitek 100 Ames) on a midstream urine sample were compared with measurement of protein concentration on that sample (n = 103). In a third study, the protein:creatinine ratio on a midstream (spot) urine sample was compared with protein excretion over the subsequent 24 hours (n = 100).

Main outcome measures: Relations between urine protein concentrations and 1. dipstick urinalysis and 2. automated urinalysis; 3. Positive and negative predictive values of spot protein:creatinine ratio for true proteinuria (> or = 300 mg/day).

Results: Automated urinalysis improved the percentage of true positive urinalyses from 48% with visual urinalysis to 74% (P = 0.02). True negatives were 98% to 100% for both methods. Spot urine protein:creatinine ratio correlated well with subsequent 24-hour urine proteinuria (r = 0.93, P < 0.001). A protein:creatinine ratio > 30 mg protein/mmol creatinine was the optimum discriminant value for true proteinuria, with sensitivity 93%, specificity 92%, positive predictive value 95% and negative predictive value 90%.

Conclusions: Use of an automated urinalysis device improved accurate detection of proteinuria, particularly reducing false positive tests. A random urine protein:creatinine ratio provides an accurate and rapid quantitation of proteinuria in hypertensive pregnant women. This should improve clinical care, especially when managing hypertensive pregnant women as outpatients.