Urinary protein/creatinine ratio in hypertensive pregnant women

Contemporary Test Performance of the Random Urine Protein-to-creatinine Ratio

OBJECTIVE

 The random urine protein-to-creatinine ratio (UPCR) is a screening test used for predicting clinically significant proteinuria (urine protein  ≥ 300 mg) during pregnancy. No consensus exists on the optimal random UPCR cutoff for performing follow-up 24 hour urine (24H) total protein collection. We aim to evaluate the test performance of random UPCR in predicting proteinuria in a contemporary cohort.

STUDY DESIGN

 This was a retrospective cohort study of pregnant patients at our institution from 2014 to 2018 with a random UPCR and follow-up 24H protein collection. The primary analysis estimated the test characteristics (sensitivity, specificity, positive and negative predictive values) of using random UPCR for the detection of proteinuria defined as urine protein ≥300 mg on 24H protein collection. UPCR cutoffs from 0.10 to 0.30 mg/dL were evaluated, receiver operator characteristic (ROC) curve was constructed, and area under the curve (AUC) was determined. A secondary analysis examined the correlation between UPCR and 24H protein using least squares regression and Pearson correlation.

RESULTS

 Paired UPCR and 24H collection results were available for 1,120 patients. Mean gestational age at time of UPCR was 31.1 ± 5.1 weeks and 687 (61.3%) of patients had a 24H ≥300 mg. UPCR <0.10 mg/dL effectively excluded proteinuria ≥300 mg on 24H collection, while UPCR ≥0.18 mg/dL correctly classifies proteinuria with 91% sensitivity, 57% specificity, 77% positive predictive value, and 79% negative predictive value. UPCR ≥1.07 mg/dL had 100% specificity for 24 hour proteinuria. The area under ROC curve was 0.86. UPCR and 24H collection were highly correlated with a Pearson correlation coefficient of 0.85. After our institution lowered the threshold to obtain a 24H from UPCR ≥0.20 mg/dL to ≥0.10 mg/dL in May 2017, the percentage of patients meeting criteria for 24H collection increased from 57.8 to 84.4%.

CONCLUSION

 The AUC and Pearson correlation suggest random UPCR is a high performance test for the prediction of proteinuria on 24H. Optimal test performance is dependent upon clinical consideration and upon the implications of the disease or condition. A random UPCR screen positive threshold of 0.18 mg/dL maximizes sensitivity to identify clinically significant proteinuria.

KEY POINTS

· Random urine protein to creatinine ratio is a high performance test for proteinuria.. · A random UPCR threshold of 0.18 mg/dL maximizes sensitivity to identify proteinuria.. · Optimal test performance is dependent on the disease or clinical condition..

A meta-analysis on diagnostic accuracy of spot urinary protein to creatinine ratio versus 12-h proteinuria in preeclampsia

To systematically review the diagnostic accuracy of spot urinary protein to creatinine ratio (PCR) and 12-h proteinuria in preeclampsia and to estimate which is a preferred alternative method for 24-h proteinuria, we carried out this meta-analysis. 25 primary studies were included based on searching strategy. For spot urinary PCR, our results showed pooled sensitivity of 87% (95% confidence interval [CI] 83%-91%) and specificity of 86% (95% CI 79%-91%), with an area under curve (AUC) of 0.93 (0.90-0.95). For 12-h proteinuria, pooled sensitivity and specificity were 92% (95% CI 87%-96%) and 99% (95% CI 75%-100%), respectively, with an AUC of 0.97 (0.95-0.98). Fagan plot and likelihood ratio scattergram showed that 12-h proteinuria yielded a better discriminatory performance on diagnosis of proteinuria (≥0.3 g/24 h). These results indicated that 12-h proteinuria estimation shows better clinical value than spot urine PCR for diagnosis of preeclampsia. However, due to the severity of condition and the fact that preeclampsia patients cannot wait for 12 h, spot urine PCR can be used as one of the diagnostic indicators.

Variation of urinary protein to creatinine ratio during the day in women with suspected pre-eclampsia

OBJECTIVE

To investigate the stability throughout the day of the protein to creatinine ratio (PCR) in spot urine, to demonstrate whether the PCR is a valid alternative for 24-hour protein investigation in pregnant women.

DESIGN

Prospective study.

SETTING

Tertiary referral university centre.

POPULATION

Women suspected of having pre-eclampsia, admitted to the Erasmus Medical Centre.

METHODS

Twenty-four-hour urine collections and simultaneously three single voided 5-ml aliquots were obtained at 8 a.m., 12 a.m. (noon) and 5 p.m. A PCR was measured in each specimen and compared with the 24-hour protein excretion.

MAIN OUTCOME MEASURES

The 24-hour proteinuria and PCR measured in spontaneous voids.

RESULTS

The PCRs correlated strongly with each other and with the 24-hour protein excretion but did show variation throughout the day (mean coefficient of variation 36%; 95% confidence interval 31-40%). The coefficient of variation was unrelated to the degree of 24-hour proteinuria. Receiver operating characteristics curves to discriminate between values below and greater than or equal to the threshold of 0.3 g protein per 24-hour had an area under the curve of respectively 0.94 (8 a.m.), 0.96 (noon) and 0.97 (5 p.m.). Sensitivities at 8 a.m., noon and 5 p.m. were respectively 89%, 96% and 94%; specificities were 75%, 78% and 78% with the proposed PCR cut-off of 30 mg/mmol (0.26 g/g) (National Institute for Health and Care Excellence guidelines).There is no evidence of a difference between the three measurement times regarding the sensitivities and specificities.

CONCLUSION

The PCR determined in spot urine varies throughout the day but is a valid alternative for 24-hour urine collections in pregnant women. It is especially useful to rapidly identify clinically relevant proteinuria.

Association of proteinuria threshold in pre-eclampsia with maternal and perinatal outcomes: a nested case control cohort of high risk women

Objectives

To evaluate occurrence of adverse maternal and perinatal outcomes with different thresholds of proteinuria (300-499mg and ≥500mg/24 hours) in pre-eclamptic women, comparing outcomes against women with chronic and gestational hypertension.

Design

Secondary analysis of the Vitamins in Pre-Eclampsia Trial.

Setting

25 UK hospitals in ten geographical areas.

Population

946 women with pre-existing risk factors for pre-eclampsia.

Methods

Women with pre-eclampsia and proteinuria 300-499mg/24h (PE300, referent group, n=60) or proteinuria ≥500 mg/24h (PE500, n=161) were compared with two groups of non-proteinuric women with chronic hypertension (CHT, n=615) or gestational hypertension (GH, n=110).

Main Outcome Measures

Maternal: progression to severe hypertension. Perinatal: small for gestational age (SGA) <5^th centile, gestation at delivery.

Results

Severe hypertension occurred more frequently in PE500 (35%) and PE300 (27%) than CHT (5.9%; P≤0.01) and GH (10%; p≤0.001). Gestation at delivery was earlier in PE500 (33.2w) than PE300 (37.3w; P≤0.001), and later in CHT (38.3w; P≤0.05) and GH (39.1w; P≤0.001). SGA infants were more frequent in PE300 (32%) than in CHT (13.3%; P≤0.001) and GH (16.5%; P≤0.05). Women in PE500 were more likely to have a caesarean section than PE300 (78% vs. 48%; P≤0.001), and to receive magnesium sulphate (17% vs. 1.7%, P≤0.05).

Conclusion

Women with PE300 have complication rates above those of women managed as out-patients (GH and CHT), meriting closer surveillance and confirming 300 mg/d as an appropriate threshold for determining in-patient management. Adverse perinatal outcomes are higher still in women with PE500.

Diagnostic accuracy of spot urinary protein and albumin to creatinine ratios for detection of significant proteinuria or adverse pregnancy outcome in patients with suspected pre-eclampsia: systematic review and meta-analysis

OBJECTIVE

To determine the diagnostic accuracy of two "spot urine" tests for significant proteinuria or adverse pregnancy outcome in pregnant women with suspected pre-eclampsia.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Searches of electronic databases 1980 to January 2011, reference list checking, hand searching of journals, and contact with experts.

INCLUSION CRITERIA

Diagnostic studies, in pregnant women with hypertension, that compared the urinary spot protein to creatinine ratio or albumin to creatinine ratio with urinary protein excretion over 24 hours or adverse pregnancy outcome. Study characteristics, design, and methodological and reporting quality were objectively assessed.

DATA EXTRACTION

Study results relating to diagnostic accuracy were extracted and synthesised using multivariate random effects meta-analysis methods.

RESULTS

Twenty studies, testing 2978 women (pregnancies), were included. Thirteen studies examining protein to creatinine ratio for the detection of significant proteinuria were included in the multivariate analysis. Threshold values for protein to creatinine ratio ranged between 0.13 and 0.5, with estimates of sensitivity ranging from 0.65 to 0.89 and estimates of specificity from 0.63 to 0.87; the area under the summary receiver operating characteristics curve was 0.69. On average, across all studies, the optimum threshold (that optimises sensitivity and specificity combined) seems to be between 0.30 and 0.35 inclusive. However, no threshold gave a summary estimate above 80% for both sensitivity and specificity, and considerable heterogeneity existed in diagnostic accuracy across studies at most thresholds. No studies looked at protein to creatinine ratio and adverse pregnancy outcome. For albumin to creatinine ratio, meta-analysis was not possible. Results from a single study suggested that the most predictive result, for significant proteinuria, was with the DCA 2000 quantitative analyser (>2 mg/mmol) with a summary sensitivity of 0.94 (95% confidence interval 0.86 to 0.98) and a specificity of 0.94 (0.87 to 0.98). In a single study of adverse pregnancy outcome, results for perinatal death were a sensitivity of 0.82 (0.48 to 0.98) and a specificity of 0.59 (0.51 to 0.67).

CONCLUSION

The maternal "spot urine" estimate of protein to creatinine ratio shows promising diagnostic value for significant proteinuria in suspected pre-eclampsia. The existing evidence is not, however, sufficient to determine how protein to creatinine ratio should be used in clinical practice, owing to the heterogeneity in test accuracy and prevalence across studies. Insufficient evidence is available on the use of albumin to creatinine ratio in this area. Insufficient evidence exists for either test to predict adverse pregnancy outcome.

Serum S100B in pregnancy complicated by preeclampsia: A case-control study

BACKGROUND

Serum S100B is a protein produced and released primarily by astrocytes of the Central Nervous System (CNS). Elevated levels of serum S100B are associated with several types of pathological conditions of the brain, including the eclampsia in pregnant women. The aim of this study was to compare serum S100B concentrations in pregnant women with severe and mild preeclampsia (PE) with S100B serum levels in normotensive pregnant women.

MATERIAL AND METHODS

Serum S100B protein was measured in normotensive pregnant women (n=15) and in women with mild PE (n=12) or severe PE (n=34). The serum S100B level (μg/L) was determined by an luminometric assay.

RESULTS

Sixty-one expectant mothers were studied, aged 26.6±8.7 (mean±SD) years and with a gestational age of 33.3±4.2 weeks. The severe PE group demonstrated higher S100B levels (0.20±0.19), as compared with mild PE (0.07±0.05) or normotensive groups (0.04±0.05).

CONCLUSION

Elevated serum S100B levels in pregnant women with severe PE suggest that some kind of neural damage and subsequent astrocytic release of S100B is not dependent on the progression from severe preeclampsia to eclampsia.

[Is morning urinary protein-to-creatinine ratio a reliable estimator of 24-hour proteinuria in patients with kidney diseases?]

INTRODUCTION

Proteinuria is the most frequent marker of kidney damage. Although 24-hour urinary proteinuria is the gold standard, the measurement of proteinuria from albumin urinary creatinine ratio is proposed as much useful method.

OBJECTIVE

To evaluate the accuracy of urine protein-to-creatinine (P/Cr) ratio in morning urine specimens as compared with 24-hour total protein excretion for the measurement of proteinuria in patients with different kidney diseases and different renal function levels.

METHODS

Proteinuria in the studied patients was assessed by 24-hour protein excretion (24-hour PRT) and spot urine P/Cr ratio. The analysis of concordance between 24-hour PRT and P/Cr was carried out using intraclass correlation coefficient (ICC), paired t-test and Bland-Altman plots. The discriminant cutoff values for spot urine P/Cr ratio in predicting 24-hour protein "threshold" excretion were determined using receiver operating characteristic curves (ROC), as well as sensitivity and specificity.

RESULTS

A total of 303 patients were included in the study. The concordance between 24-hour PRT and P/Cr ratio was excellent (ICC 0.931). Systematic overestimation of PRT by urinary P/ Cr ratio was disclosed (mean difference 0.138, p = 0.011). The P/Cr of 0.25 (sensitivity 0.90; specificity 0.96), 0.66 (1.00; 0.91) and 2.55 (1.0; 0.97) g/g reliably predicted 24-hour urine total protein equivalent "thresholds" at 0.2, 1.0 and 3.5 g/day. The chronic renal failure group independently positively influenced the difference between 24-hour PRT and P/Cr. It means the lower the kidney function the higher is the difference between the two proteinuria measurements.

CONCLUSION

This study supports the recommendation of using spot urine P/Cr ratio in proteinuria screening in patients with different kidney diseases. The obtained results indicated better agreement between morning P/Cr and 24-hour PRT in patients with lower proteinuria and better kidney function.

Protein/creatinine ratio on random urine samples for prediction of proteinuria in preeclampsia

OBJECTIVE

To evaluate Protein/Creatinine ratio on random urine samples for prediction of proteinuria in preeclampsia.

MATERIALS AND METHODS

This study was performed on 150 pregnant women who were hospitalized as preeclampsia in Ghaem Hospital during 2006. At first, a 24-hours urine sample was collected for each patient to determine protein/creatinine ratio. Then, 24-hours urine collection was analyzed for the evaluation of proteinuria. Statistical analysis was performed with SPSS software.

RESULTS

A total of 150 patients entered the study. There was a significant relation between the 24-hours urine protein and protein/creatinine ratio (r = 0.659, P < 0.001).

CONCLUSION

Since the measurement of protein/creatinine ratio is more accurate, reliable, and cost-effective, it can be replaced by the method of measurement the 24-hours urine protein.

Protein creatinine ratio in random urine sample of hypertensive pregnant women: maternal and perinatal outcomes

Objective. To compare protein/creatinine ratio (PCR) in random urine sample levels and adverse outcomes in hypertensive pregnant women. Methods. A total of 370 medical charts from hypertensive pregnant women were reviewed and stratified into three groups according to different PCR in random urine sample levels (group 1: PCR < 0.3 mg/mg; group 2: PCR 0.3-1.99 mg/mg; group 3: PCR ≥ 2.0 mg/mg) and compared with composite maternal and perinatal outcomes. Those outcomes were severe hypertension, thrombocytopenia, high lactate dehydrogenase count, disseminated intravascular coagulation, abruptio placentae, HELLP (hemolysis, elevated liver enzymes, low platelet count) syndrome, eclampsia, perinatal death, newborn cerebral hemorrhage, respiratory distress syndrome of newborn, neonatal sepsis, and newborn small for gestational age. Results. To obtain a composite maternal adverse outcome the odds ratio [ORs] between PCR groups were 1.8 (95% confidence interval [CI]: 1.1-3.2) between groups 1 and 2, and 3.1 (95% CI: 1.5-6.3) between groups 1 and 3; for composite perinatal adverse outcomes, the ORs were 3.0 (95% CI: 1.5-5.9) between groups 1 and 2, and 3.4 (95% CI: 1.6-7.5) between groups 1 and 3. Conclusions. Hypertensive pregnant women with a PCR ≥ 0.3 mg/mg, had worse maternal and perinatal outcomes than those with PCR < 0.3 mg/mg. Above the cut-off of 0.3 mg/mg, higher PCRs are not associated with a significant increase in maternal and perinatal morbidity.

Increases in urinary creatinine and blood pressure during early pregnancy in pre-eclampsia

BACKGROUND

It is important to predict the development of pre-eclampsia (PE) during early pregnancy to prevent its occurrence later on. In this study, we studied urinary biochemical parameters and blood pressure (BP) during and after pregnancy to find useful parameters for predicting PE.

METHODS

A case-control study was performed in 25 PE patients and 172 normotensive pregnant women. Twelve biochemical parameters were measured in spot urine, and the systolic and diastolic BPs were measured using an automated device during pregnancy and six to eight weeks after birth.

RESULTS

A multiple logistic regression analysis showed that the combinations of urinary creatinine (Cr) and systolic BP (SBP) in the first trimester of pregnancy (8.9 +/- 2.6 weeks), and of urinary inorganic phosphorus (IP)/Cr and SBP in the second trimester of pregnancy (19.0 +/- 1.6 weeks) were useful for predicting PE. The area under the curve in the receiver operator characteristic curve of the combination of urinary Cr and SBP in the first trimester was 0.85 (95% confidence interval [CI] 0.74-0.96), and that of the combination of urinary IP/Cr and SBP in the second trimester was 0.91 (95% CI: 0.86-0.97). When used 249 mg/dL in urinary Cr and 128 mmHg in SBP as their cut-off points, the combination in the first trimester increased the accuracy (sensitivity 75% and specificity 95%) in predicting PE, as compared with that of urinary Cr (29%, 99%) or SBP (50%, 98%).

CONCLUSIONS

Combination of urinary Cr and SBP in early pregnancy and that of urinary IP/Cr and SBP in mid-pregnancy are useful for the prediction of PE.

Interpreting abnormal proteinuria in pregnancy: the need for a more pathophysiological approach

This review and opinion article focuses on the definitions and meanings of abnormal protein excretion in pregnancy, asking the following questions: Are our tests to determine abnormal proteinuria adequately performed? Are current guidelines for diagnosis of excessive proteinuria, especially when used to identify preeclampsia, supported by adequate data? Can the magnitude of proteinuria be used as a reliable clinical biomarker of the gravity of preeclampsia? Should timed urine collections, primarily 24-hour excretions, be supplanted by the urine protein/creatinine ratio in clinical practice? The answers to most of these questions are: We are not sure, or some guidelines are poorly supported by data and may prove erroneous. We suggest a more physiologic approach to assessment of proteinuria and believe that if clinicians and investigators looked at proteinuria in terms of how the kidney handles protein in health and disease it would lead to a more rational and evidence-based approach to proteinuria in pregnancy. Finally, we recommend that current cutoff for abnormal proteinuria be used to diagnose preeclampsia, but the level of proteinuria should not guide management. Other variables, such as status of blood pressure control, evidence of increasing organ damage in the liver and hematological systems, evidence of falling glomerular filtration rate, and signs of neurological involvement, are more reliable indicators of severity of preeclampsia.

A Prospective Study of the Impact of Automated Dipstick Urinalysis on the Diagnosis of Preeclampsia

OBJECTIVE

To determine prospectively in hypertensive pregnant women 1) the accuracy of dipstick testing for proteinuria using automated urinalysis, 2) factors that might affect such accuracy, and 3) the potential impact of automated dipstick testing on the accuracy of diagnosis of preeclampsia according to acceptance of proteinuria at either 1 + or 2 + level.

DESIGN

Prospective study.

SETTING

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

POPULATION

170 hypertensive pregnant women attending as outpatients or inpatients.

METHODS

503 midstream urine samples were collected prospectively on separate occasions from 170 women. Full urinalysis was recorded using the Bayer Clinitek 50 automated urinalysis device and Multistix 10SG urinalysis strips (Bayer Diagnostics, Victoria, Australia). Each MSU was analysed for spot protein/creatinine ratio and also for culture and sensitivity if symptoms of a urinary tract infection were present or dipstick included positive nitrites. Urinalysis protein results were compared with spot urinary protein/creatinine ratio (previously shown to correlate with 24-hr urine protein excretion) to determine the accuracy of urinalysis. True proteinuria was defined as a ratio >/= 30 mg protein/mmol creatinine.

RESULTS

False positive dipstick tests ranged from 7% at 3 + level to 71% at 1 + proteinuria level while false negative rates were 7% for "nil" and 14% for "trace" proteinuria, 9% overall. Accepting the dipstick proteinuria result at face value led to an incorrect diagnosis of preeclampsia or gestational hypertension in 85 (50%) women. Dipstick proteinuria was significantly more likely to be correct (true positive/true negative) if diastolic blood pressure was elevated > 90 mmHg (p = 0.032) and in the absence of ketonuria (p = 0.001). Accepting a diagnosis of preeclampsia on the basis of de novo hypertension and dipstick testing alone was accurate less often (70%) when > 1 + was used as a discriminant value than at the 82% of presentations when > 2 + was used (p = 0.001).

CONCLUSION

Accepting "nil" or "trace" proteinuria as a true negative dipstick results fails to identify approximately 1 in 11 hypertensive pregnant women with true proteinuria, a false negative rate that may be acceptable provided these women are subject to ongoing vigilant clinical review. Even with automated urinalysis the false positive rate for dipstick levels >/= 1 + is very high, particularly in the presence of ketonuria and relying on this alone to diagnose preeclampsia leads to significant errors in diagnosis. Accepting >/= 2 + dipstick proteinuria improves overall diagnostic accuracy for preeclampsia at the expense of a higher false negative rate. This study emphasizes the need to confirm dipstick proteinuria with a further test such as a spot urine protein/creatinine ratio in all hypertensive pregnant women, particularly in research studies.

Variation in the Urinary Protein/Creatinine Ratio at Four Different Periods of the Day in Hypertensive Pregnant Women

OBJECTIVE

To assess the urine protein/creatinine ratio in urine samples of pregnant women with hypertension in regard to: 1) the presence of significant variation at different periods of the day; 2) the differences if they exist, to identify the most reliable period of the day for sampling; and 3) whether the first sample, obtained when the patient arrives at the clinic, correlates with the same accuracy, with the 24-hour proteinuria.

DESIGN

Cross-sectional study.

PLACE

Obstetrics Emergency Department, Hospital de Clínicas de Porto Alegre, a teaching hospital in Porto Alegre, Brazil.

POPULATION

Seventy-five women with hypertension with 20-week gestation or over.

METHODS

Urine samples for determination of the protein/creatinine ratio were obtained on arrival (first specimen) and every 6 hours thereafter, totaling four samples in 24 hours. Four sampling periods were established: 1) from 8 am to 2 pm, 2) from 2 pm to 8 pm, 3) from 8 pm to 2 am, and 4) from 2 am to 8 am. The protein/creatinine ratio in the four different day periods were compared with the 24-hour proteinuria obtained simultaneously. The results were analyzed by the Spearman correlation and the receiver-operator characteristic (ROC) curve.

RESULTS

The urine protein/creatinine ratio is strongly correlated (Spearman correlation equal to 0.8 or greater) with the 24-hour proteinuria at all four periods of the day (p<0.001), as well as the first sample obtained on arrival (p=0.003). These findings were corroborated by the ROC curve in which the values of four day periods and that of the first sample were equal to or greater than 0.930.

CONCLUSION

In hypertensive pregnant women, the single voided urine sample protein/creatinine ratio, irrespective of sampling time, is strongly correlated with the 24-hour proteinuria, as is the sample obtained on arrival.

The 24-hour urine collection: gold standard or historical practice?

OBJECTIVE

The objective of the study was to determine completeness of 24-hour urine collection in pregnancy.

STUDY DESIGN

This was a retrospective laboratory/chart review of 24-hour urine collections at British Columbia Women's Hospital. Completeness was assessed by 24-hour urinary creatinine excretion (UcreatV): expected according to maternal weight for single collections and between-measurement difference for serial collections.

RESULTS

For 198 randomly selected pregnant women with a hypertensive disorder (63% preeclampsia), 24-hour urine collections were frequently inaccurate (13-54%) on the basis of UcreatV of 97-220 micromol/kg per day (11.0-25.0 mg/kg per day) or 133-177 micromol/kg per day (15.1-20.1 mg/kg per day) of prepregnancy weight (respectively). Lean body weight resulted in more inaccurate collections (24-68%). The current weight was frequently unavailable (28%) and thus not used. For 161 women (81% proteinuric) with serial 24-hour urine levels, a median [interquartile range] of 11 [5-31] days apart, between-measurement difference in UcreatV was 14.4% [6.0-24.9]; 40 women (24.8%) had values 25% or greater, exceeding analytic and biologic variation.

CONCLUSION

Twenty-four hour urine collection is frequently inaccurate and not a precise measure of proteinuria or creatinine clearance.

A practical approach to using spot urine protein/creatinine ratios for assessing proteinuria in pregnancy

OBJECTIVE

The aim of this study is to assess the diagnostic accuracy of the spot urine protein/creatinine ratio compared with the 24-hour urine protein in pregnancy.

STUDY DESIGN

In this prospective cohort study of inpatient pregnant women, the protein/creatinine ratio and dipstick protein were assessed from a single urine sample collected at the start of the 24-hour urine. Both tests were compared with the 24-hour urine protein for correlation and test characteristics.

RESULTS

In the 196 specimens analysed, we found a strong correlation between the spot urine protein/creatinine ratio and 24-hour urine protein (r (2) = 0.78, P < 0.01). A protein/creatinine ratio <0.1 ruled out significant proteinuria (≥300 mg/day) with sensitivity and negative predictive value 100%. A protein/creatinine ratio ≥0.4 detected significant proteinuria (specificity and positive predictive value of 100%). A protein/creatinine ratio ≥4.6 had a specificity and positive predictive value of 100% for detecting severe proteinuria (≥5000 mg/day). Urine dipsticks correlated poorly with the 24-hour urine protein (r (2) = 0.40, P = 0.826). Nineteen percent of dipsticks reading nil or trace were false-negative results.

CONCLUSION

The spot urine protein/creatinine ratio correlated well with the 24-hour urine protein and performed better than the urine dipsticks. Significant proteinuria in pregnancy was excluded if the protein/creatinine ratio was <0.1 and identified when it was ≥0.4.

Protein/creatinine ratio in preeclampsia: a systematic review

OBJECTIVE

To estimate the accuracy of the protein/creatinine ratio in predicting 300 mg of protein in 24-hour urine collection in pregnant patients with suspected preeclampsia.

DATA SOURCES

Articles were identified through electronic databases (MEDLINE, CINHAL, and Cochrane) using the terms "preeclampsia," "protein/creatinine ratio," and "diagnosis," during the period January 1966 to October 2007. The relevant citations were hand searched.

METHODS OF STUDY SELECTION

Included studies evaluated patients for suspected preeclampsia with a 24-hour urine sample and a protein/creatinine ratio. Only English-language articles were included. Studies including patients with only chronic illness such as chronic hypertension, diabetes mellitus, or renal impairment were excluded. Using the Quality Assessment of Diagnostic Accuracy Studies questionnaire, we created group 1 satisfying all the required criteria and group 2 not satisfying all of it. Two researchers independently extracted the accuracy data. A graph comparing six receiver operating characteristic curves was plotted.

TABULATION, INTEGRATION, AND RESULTS

Twenty-one studies were identified, but only seven met our inclusion criteria (1,717 total patients). Group 1, with three studies, had 510 patients. The studies evaluated different cut points for positivity of protein/creatinine ratio from 130 mg/g to 700 mg/g. For protein/creatinine ratio 130-150 mg/g, sensitivity ranged from 90-99%, and specificity ranged from 33-65%; for protein/creatinine ratio 300 mg/g, sensitivity ranged from 81-98% and specificity ranged from 52-99%; for protein/creatinine ratio 600-700 mg/g, sensitivity ranged from 85-87%, and specificity ranged from 96-97%.

CONCLUSION

Random protein/creatinine ratio determinations are helpful primarily when they are below 130-150 mg/g, in that 300 mg or more proteinuria is unlikely below this threshold. Midrange protein/creatinine ratio (300 mg/g) has poor sensitivity and specificity, requiring a full 24-hour urine for accurate results. Higher thresholds have not been adequately studied.

Diagnostic accuracy of the protein/creatinine ratio in urine samples to estimate 24-h proteinuria in patients with primary glomerulopathies: a longitudinal study

BACKGROUND

The protein/creatinine (P/C) ratio in urine samples has been used in the clinical management of patients with glomerular diseases. The aim of this study is to perform a prospective evaluation of the P/C ratio accuracy in determining critical levels of proteinuria in patients with glomerulopathies.

METHODS

This is a longitudinal study of 41 adult patients with primary glomerulopathies treated with immunosuppressive drugs or angiotensin-converting enzyme inhibitors in a 6-month follow-up. Correlation and agreement level between P24 and the P/C ratio were evaluated. Kappa statistic was employed to evaluate concordance between the two methods taking into account clinically relevant categories of proteinuria. ANOVA for repeated measures was employed. Diagnostic accuracy of the P/C ratio was evaluated by receiver-operator curves (ROC).

RESULTS

There was a significant correlation between P24 and the P/C ratio during the 6-month period (P < 0.001 in all time points). Mean differences between P24 and P/C ratios at baseline and from the first to the sixth month were 2.00, 1.88, 1.22, 1.07, 0.65, 0.34 and 0.57 respectively. In spite of the lower agreement between P24 and the P/C ratio for higher levels of proteinuria, we found substantial Kappa values for categories of proteinuria in all periods. ROC considering the cut-off levels of 0.20 g and 3.5 g for P24 showed that the P/C ratio had a very good accuracy, with areas under the curve of 0.99 (95% CI: 0.97-1.00) and 0.99 (95% CI: 0.99-1.00), respectively.

CONCLUSION

This longitudinal analysis corroborates the findings of previous cross-sectional studies, supporting the use of the P/C ratio as an accurate test to define critical levels of proteinuria.

Comparison of methods to identify significant proteinuria in pregnancy in the outpatient setting

The efficacy of the albumin/creatinine ratio (ACR) measurement in detection of significant proteinuria when performed in a high-risk antenatal clinic was compared with automated dipstick, protein/creatinine ratio (PCR), and 24-hour urine protein measurements. Both the ACR (DCA 2000) and PCR were strongly predictive for the presence or absence of significant proteinuria, with positive likelihood ratios (LRs) of 27.4 and 31.6 and negative LRs of 0.0 and 0.1, respectively. Both the ACR (DCA 2000) and PCR are effective tests for both identifying and excluding significant proteinuria in the outpatient setting. The ACR (DCA 2000) has the advantage of providing an immediate result.

Protein:creatinine ratio in random urine samples is a reliable marker of increased 24-hour protein excretion in hospitalized women with hypertensive disorders of pregnancy

BACKGROUND

The protein:creatinine ratio in random, untimed urine samples correlates with 24-h protein excretion in pregnant women with and without hypertension. Nevertheless, whether this ratio is appropriate as a screening test for proteinuria is still unclear, in part because of the paucity of large studies.

METHODS

We measured protein:creatinine ratios in random urine samples and protein contents of 24-h urine samples in a cross-sectional study of 927 hospitalized pregnant women at >/=20-weeks of gestational age and in a 2nd cohort of 161 pregnant women. In the 2nd group, urine specimens were obtained before and after completion of the 24-h collections, avoiding 1st-morning void specimens.

RESULTS

Protein excretion was >/=300 mg/24 h in 282 patients (30.4%). The urine protein:creatinine ratio and the 24-h protein excretion were significantly correlated (r = 0.98, P <0.001). The protein:creatinine ratio as an indicator of protein excretion >/=300 mg/24 h was >/=0.3. The sensitivity and specificity were 98.2% and 98.8%, respectively. Positive and negative predictive values were 97.2% and 99.2%, respectively, and positive and negative likelihood ratios were 79.2 and 0.02, respectively. The diagnostic accuracy of the urinary protein:creatinine ratio was corroborated in the 2nd cohort of patients, which also showed no statistically significant difference in protein:creatinine ratio between samples obtained >24 h apart.

CONCLUSIONS

Random urinary protein:creatinine ratio is a reliable indicator of significant proteinuria (>300 mg/day) in nonambulatory pregnant women, irrespective of sampling time during the daytime. The protein:creatinine ratio may be reasonably used as an alternative to the 24-h urine collection method.

Predicting proteinuria in hypertensive pregnancies with urinary protein-creatinine or calcium-creatinine ratio

OBJECTIVE

Evaluate the value of random urinary protein-creatinine (PrCr) and calcium-creatinine (CaCr) ratios to predict 24-h proteinuria in hypertensive pregnancies.

STUDY DESIGN

Spot urine samples were collected before routine 24-h urine collections from consecutive pregnant women with hypertension (n=83). Reliability of spot urinary PrCr and CaCr to detect significant proteinuria (>or=300 mg/day) using 24-h urine protein as 'gold-standard' was assessed by receiver-operating characteristic (ROC) curve.

RESULTS

Fifty-one patients (61.4%) had significant proteinuria (45 pre-eclampsia, 5 superimposed pre-eclampsia, 1 renal hypertension). Area under ROC curve to predict proteinuria was 0.82 (95% confidence interval (CI) 0.73 to 0.92, P<0.001) for PrCr and 0.55 (95% CI 0.43 to 0.68, P=0.2) for CaCr. A cutoff value of >0.19 for PrCr best predicted significant proteinuria with sensitivity, specificity, positive and negative predictive values and likelihood ratios (positive and negative), respectively, of 80.4, 68.8, 80.4, 68.8%, 2.57 and 3.51.

CONCLUSION

Spot urinary PrCr predicts total urinary protein excretion in hypertensive pregnancies.

Usage of spot urine protein to creatinine ratios in the evaluation of preeclampsia

OBJECTIVE

The objective of the study was to prospectively compare spot urine protein to creatinine (P:C) ratios with 24 hour urine collections for protein in women being evaluated for preeclampsia.

STUDY DESIGN

A spot urine P:C ratio was obtained at the beginning of 24 hour urine collections from 126 patients admitted to evaluate for preeclampsia. Correlation between the spot P:C ratio with the 24 hour urine collections was calculated. Receiver operator characteristic curves were constructed to determine best P:C cut-offs for 300 mg and 5000 mg protein per 24 hours.

RESULTS

Random spot P:C ratios were strongly correlated with 24 hour urine protein levels (Pearson r = 0.88). The optimal P:C cut-offs were 0.21 (300 mg per 24 hours) and 3.0 (5000 mg per 24 hours). A P:C ratio of less than 0.21 (300 mg per 24 hours) had a negative predictive value (NPV) of 83.3% and a P:C ratio of less than 3.0 (5000 mg per 24 hours) had 100% NPV.

CONCLUSION

Urine spot P:C ratio correlated well with 24 hour urine collections for protein but was not justified as a substitute for timed collections.

Random albumin/creatinine ratio for quantification of proteinuria in manifest pre-eclampsia

OBJECTIVE

1) To assess the correlation between urine albumin/creatinine ratio (ACR) and 24-hour urine albumin excretion in women with pre-eclampsia, 2) to study the influence of potential confounders on this correlation and 3) to assess the variability of ACR between voids during a 24-hour period.

DESIGN

Prospective study.

SETTING

Fetal maternity ward, university hospital.

POPULATION

Women with pre-eclampsia scheduled for quantitative albumin measurement with a 24-hour urine collection.

METHODS

Random urine samples were obtained for analysis of ACRs during the time of 24-hour urine collections in 31 women. ACRs were also measured from the complete 24-hour collections. In five additional women, serial urine samples were obtained during the 24-hour collection.

MAIN OUTCOME MEASURES

Correlation between ACRs and albumin amount in 24-hour urine samples. Variability of the ACRs during a 24-hour collection.

RESULTS

The random ACR was poorly correlated to 24-hour excretion of urine albumin (R(2)= 0.42). Adjustment for maternal age and nifedipine medication significantly (P= 0.044 and P= 0.023, respectively) improved the correlation (R(2)= 0.60). The mean variability (highest/lowest) of ACR during a 24-hour period was 222%. The ACR from the 24-hour collection had an excellent correlation to 24-hour excretion of urine albumin (R(2)= 0.96).

CONCLUSIONS

In women with pre-eclampsia, random ACR is not stable during the day and cannot predict 24-hour urine protein excretion accurately. ACR from the 24-hour collection is an accurate predictor of total albumin amount and can be used to minimise errors from incomplete collections.

Use of protein:creatinine ratio measurements on random urine samples for prediction of significant proteinuria: a systematic review

BACKGROUND

Proteinuria is recognized as an independent risk factor for cardiovascular and renal disease and as a predictor of end organ damage. The reference test, a 24-h urine protein estimation, is known to be unreliable. A random urine protein:creatinine ratio has been shown to correlate with a 24-h estimation, but it is not clear whether it can be used to reliably predict the presence of significant proteinuria.

METHODS

We performed a systematic review of the literature on measurement of the protein:creatinine ratio on a random urine compared with the respective 24-h protein excretion. Likelihood ratios were used to determine the ability of a random urine protein:creatinine ratio to predict the presence or absence of proteinuria.

RESULTS

Data were extracted from 16 studies investigating proteinuria in several settings; patient groups studied were primarily those with preeclampsia or renal disease. Sensitivities and specificities for the tests ranged between 69% and 96% and 41% and 97%, respectively, whereas the positive and negative predictive values ranged between 46% and 95% and 45% and 98%, respectively. The positive likelihood ratios ranged between 1.8 and 16.5, and the negative likelihood ratios between 0.06 and 0.35. The cumulative negative likelihood ratio for 10 studies on proteinuria in preeclampsia was 0.14 (95% confidence interval, 0.09-0.24).

CONCLUSION

The protein:creatinine ratio on a random urine specimen provides evidence to "rule out" the presence of significant proteinuria as defined by a 24-h urine excretion measurement.

Proteinuria in pre-eclampsia: how much matters?

OBJECTIVE

To determine, in women with proteinuric pre-eclampsia, whether a discriminant value of proteinuria at the time of diagnosis predicts the presence or absence of subsequent adverse maternal and fetal outcomes.

DESIGN

Retrospective cohort study.

SETTING

One teaching hospital and two primary referral hospitals in Sydney, Australia.

SAMPLE

Three hundred and twenty-one pregnant women with proteinuric pre-eclampsia, managed according to a uniform management protocol.

METHODS

All women with the diagnosis of proteinuric pre-eclampsia in the years 1998-2001 were studied. After exclusion of women with pre-eclampsia superimposed on pre-existing hypertension, a twin pair, unavailable spot urine results, 353 women were analysed using logistic regression to determine separately the predictors of any adverse maternal or fetal outcomes at the time of delivery. Receiver operating characteristic (ROC) curves, sensitivity and specificity were then calculated from the data.

MAIN OUTCOME MEASURES

Adverse maternal outcomes: severe maternal hypertension (BP > or = 170/110 mmHg), renal insufficiency, liver disease, cerebral irritation, haematological disturbances. Adverse fetal outcomes: small for gestational age, perinatal mortality.

RESULTS

There were 108 (34%) adverse maternal outcomes and 60 (19%) adverse fetal outcomes including two stillbirths. In multivariate analysis, an adverse maternal outcome was significantly associated with higher spot urine protein/creatinine ratio at diagnosis (P < 0.0001) with an odds ratio (OR) of 1.003 per mg/mmol (95% confidence interval [CI] 1.002-1.004) and with older maternal age (P= 0.014) with OR 1.06 per year (95% CI 1.01-1.11). An increased risk of adverse fetal outcome was associated with higher spot urine protein/creatinine (P= 0.013; OR 1.44 per log [mg/mmol], 95% CI 1.08-1.92), gestation at diagnosis <34 weeks (P < 0.0001; OR 3.60, 95% CI 1.90-6.82) and early pregnancy systolic blood pressure < or =115 mmHg (P= 0.0002; OR 3.41, 95% CI 1.77-6.57). The area under the receiver operating characteristic (ROC) curve was 0.67 for adverse maternal outcomes and 0.72 for adverse fetal outcomes.

CONCLUSIONS

With increasing proteinuria, there is increased risk of adverse maternal and fetal outcomes. Although we did not identify a specific spot protein/creatinine ratio that could be used as a definitive screening value for adverse outcomes, it is possible to utilise data from this study to predict the likelihood of adverse maternal and fetal outcomes. A high spot urine protein/creatinine ratio in pre-eclamptic women of greater than 900 mg/mmol ( approximately 9 g/day), or greater than 500 mg/mmol (approximately 5 g/day) in women over 35 years, is associated with a greatly increased likelihood of adverse maternal outcomes.

Accuracy of urinalysis dipstick techniques in predicting significant proteinuria in pregnancy

OBJECTIVE

To estimate the accuracy of point-of-care dipstick urinalysis in predicting significant proteinuria in pregnancy.

DATA SOURCES

Literature from 1970 to February 2002 was identified via 1). general bibliographic databases, that is, MEDLINE and EMBASE, 2). Cochrane Library and relevant specialist register of the Cochrane Collaboration, and 3). checking the reference lists of known primary and review articles.

METHODS OF STUDY SELECTION

Studies were selected if the accuracy of dipstick urinalysis techniques in predicting total protein excretion was estimated compared with a reference standard (laboratory estimation of protein excretion). The tests included visually read color-change dipsticks and automated dipstick urinalysis. Study selection, quality assessment, and data abstraction were performed independently and in duplicate.

TABULATION, INTEGRATION, AND RESULTS

Data from selected studies were abstracted as 2 x 2 tables comparing the test result with the reference standard. Test accuracy was expressed as likelihood ratios. Summary likelihood ratios were generated as measures of diagnostic accuracy to determine posttest probabilities. The electronic search produced 1543 citations. After independent review of published articles, a total of 34 articles was obtained for further scrutiny, and 7 studies were considered eligible for inclusion in the review. The 6 studies evaluating visual dipstick urinalysis produced a pooled positive likelihood ratio of 3.48 (95% confidence interval 1.66, 7.27) and a pooled negative likelihood ratio of 0.6 (95% confidence interval 0.45, 0.8) for predicting 300 mg/24-hour proteinuria at the 1+ or greater threshold.

CONCLUSION

The accuracy of dipstick urinalysis with a 1+ threshold in the prediction of significant proteinuria is poor and therefore of limited usefulness to the clinician. Accuracy may be improved at higher thresholds (greater than 1+ proteinuria), but available data are sparse and of poor methodological quality. Therefore, it is not possible to make meaningful inferences about accuracy at higher urine dipstick thresholds. There is an urgent need for research in this area of common obstetric practice.

Management and monitoring of severe preeclampsia

Preeclampsia is associated with increased maternal and perinatal morbidity and mortality. Preeclampsia is more than pregnancy-induced hypertension. The hypertension is only one manifestation of an underlying multifactorial, multisystem disorder, initiated early in pregnancy. In established severe disease there is volume contraction, reduced cardiac output, enhanced vascular reactivity, increased vascular permeability and platelet consumption. Medical treatment of severe hypertension in pregnancy is required. The more controversial issues are the role of pharmacological treatment in conservative management of severe preeclampsia aiming at prolongation of pregnancy, the ability of such therapy to modify the course of the underlying systemic disorder and the effects on fetal and maternal outcome. This paper presents an overview concerning the current developments in management and monitoring of severe preeclampsia. Controversial topics such as the role of plasma volume expansion in preeclampsia, expectant versus aggressive management of severe preeclampsia remote from term, and pharmacological interventions in the management of eclampsia and the HELLP syndrome are addressed.