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 I. 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 pr0tein:creatinine ratio on a midstream (spot) urine sample was compared with protein excretion over the subsequent 24 hours (n = 100). Main outcome measuresRelations 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 (2 300 mglday).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 pr0tein:creatinine ratio > 30 mg proteidmmol creatinine was the optimum discriminant value for true proteinuria, with sensitivity 93%, specificity 92%, positive predictive value 95% and negative predictive value 90%.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. Conclusions

Urinalysis vs urine protein–creatinine ratio to predict significant proteinuria in pregnancy

“…For example, automated dipstick urinalysis is more specific for predicting 24-h proteinuria than is ward dipstick urinalysis. 6 Furthermore, discrepancies in the reported sensitivity and specificity of the dipstick urinalysis may be due to differences in the spectrum of illness in the populations studied or the time of day that the spot urine was collected.…”

Urinary Dipstick Proteinuria Testing: Does Automated Strip Analysis Offer an Advantage Over Visual Testing?

“…[6][7][8][9] Our specificities were high for both visually read (95.3%) and automated dipstick (97.3%) testing compared with published values (84% for visual and 37% to 100% for automated testing). [5][6][7][8][9] We are aware of two studies that directly compared the diagnostic test properties of visual dipstick testing with automated testing. A strength of our study is that we assessed a broad spectrum of high-risk patients with and without significant proteinuria (diagnosed by a random urinary PrCr of ≥ 30 mg/mmol), consistent with published recommendations.…”

“…We used the Urisys 1100 analyzer because we were able to adjust (and maximize) sensitivity; as a result, we had to use the Chemstrip 10A strips and could not use the Multistix 10SG strips (the strips used for visual analysis in the clinic) because these must be analyzed using the Clinitek automated reader (Siemens Healthcare Diagnostics, Inc., Tarrytown, NY) which does not have adjustable parameters. 7,8 It is possible, therefore, that sensitivity with the automated urinary dipstick analysis could have been higher if we had used the Multistix 10SG strips; this was the case when use of Multistix 10SG strips was compared with Chemstrip 10A strips on older automated laboratory strip readers. 17 …”

“…5 Diagnostic test performance of visually read dipstick proteinuria measurement may be improved with use of an automated test strip reader. In theory, automation may also reduce subjectivity; nevertheless, published sensitivities (41%, 6 82%, 7 90%, 8 and 100% 9 ) and corresponding specificities (100%, 81%, 86%, and 37%) for automated reading have varied widely, even when the prevalence of proteinuria in the study populations was similar (i.e., 45% 7 and 48% 6 ).…”

“…10 Two studies have compared the diagnostic test properties of automated screening with visually read urinary test strips for proteinuria. 7,8 Although one study compared test strip screening with 24-hour urinary protein excretion (g/d) 7 and the other used 24-hour urinary protein concentration (g/L) as the comparator, 8 both studies demonstrated superior diagnostic test properties of automated testing compared with visual.…”