Objective(s):To assess the diagnostic accuracy of spot urine protein-creatinine (P/C) ratio and its compareson with 24-hour urine proteinuria for predicting eclampsia. Method(s): Spot urine P/C ratio was determined in a mid-stream urine sample, and the 24-hour urine protein was measured. The correlation between the spot P/C ratio and 24-hour urine protein amount was done. Logistic regression analysis and ROC curve analysis have been used to analyse data. Result(s): There was a strong correlation between the spot P/C ratio and 24-hour urine protein excretion (pearson’s correlation coefficient r = 0.71; P < 0.0001). The optimal spot P/C ratio cutoff point was 0.25, for 300 mg/24 h of protein excretion, with sensitivity and specificity of 69% and 75% respectively. Conclusion(s): Spot urine P/C ratio is a quick and reliable tool which can be used as an alternative method for evaluation of proteinuria for diagnosis of pre-eclampsia.
Pre-eclampsia is a multisystem disorder complicating 5% - 10% of pregnancy [1]. Pre-eclampsia is a major cause of maternal and fetal morbidity and mortality in India. This is a pregnancy specific syndrome of reduced organ perfusion secondary to vasospasm and endothelial activation [2]. The minimum criteria for the diagnosis of pre-eclampsia are hypertension plus proteinuria. Proteinuria is an important sign of pre-eclampsia. Significant proteinuria is described as 300 mg or more of urine protein per 24 hours period. The gold standard for diagnosis of significant proteinuria is 24 hours urine collections [3].
However the collection of urine for 24 hours is timeconsuming and needs strong co-operation; requires hospitalization, inconvenient, costly and inaccurate due to incomplete collection and poor compliance. This can delay diagnosis and management of pre-eclampsia.
A more rapid test capable of accurately predicting end results of 24 hours urine is required. An alternative method for quantitative evaluation of proteinuria is the measurement of protein-creatinine ratio in spot urine sample, which avoids the influence of variation in urinary solute concentration and provides a more convenient and rapid method to assess protein excretion [4]. A rapid and accurate test may provide efficient in-patient and outpatient monitoring of proteinuria and may shorten the duration of hospitalization. This study was conducted to assess the diagnostic accuracy and determine an optimum cut-off point of spot urine protein-creatinine ratio for the prediction of significant proteinuria in patients with pre-eclampsia.
2. MATERIAL AND METHODS
The present study was planned as a prospective study which include 140 pregnant women of >20 weeks of gestation period and >140/90 mmhg Blood pressure, admitted in Upper India Sugar Exchange, Dept. of Gynaecology, G.S.V.M. Medical College, Kanpur over a period of 18 months during January, 2009 to June, 2010.
A detailed history with thorough clinical examination and routine investigations, liver function test, renal function test was done to select women. Women with chronic hypertension, intrinsic renal disease, liver disease, coexisting urinary tract infection, Gestational diabetes mellitus, Inadequate specimen, Heavy exercise—more than 1hour, Bacteremia, Strict bed rest longer than 24 hours were excluded from the study.
All women included in the study irrespective of the severity of disease were asked to provide spot mid stream urine sample and collect all the urine subsequently for 24 hours period. The urine protein-creatinine ratio was determined on spot urine specimen. Total urine protein quantification was done by well established, Biuret calorimetric assay and urine-creatinine estimation was done by modified Jaffe’s method. The urine P/C ratio was obtained by dividing the total urine protein concentration by the urine creatinine concentration.
The relationship between protein-creatinine ratio and 24-hour protein excretion was assessed by Pearson correlation coefficient. Sensitivity, specificity, positive predictive value and negative predictive value of random urine protein creatinine ratio at various cut offs for prediction of significant proteinuria were estimated with a 95% confidence interval (95% CI), using the results of 24-hour urine collection as gold standard.
The received operating characteristic (ROC) curve analysis was used to determine the best discriminator values of the spot urine protein-creatinine ratios for preeclampsia (proteinuria >300 mg/24 hr). A P value of 0.05 was considered to be significant. The SPSS software was used for the statistical analyses.
3. RESULTS
In this study a total of 126 pregnant women with preeclampsia were selected according to the inclusion and exclusion criteria.14 were excluded from the study, 7 were delivered before completion of 24 hour urine collection, 3 were diagnosed with chronic hypertension and 4 were having urinary tract infection.
Table 1 shows age group 21 to 30 years contributed the highest percentage (87.92%). Majority of subjects were nulliparous (46.03%), followed by primipara (19.04%). Majority of subjects having high blood pressure were belong to group 28 to 32 week gestational age (42.06%), followed by group 33 to 36 weeks gestational age (31.74%). Mean systolic blood pressure was 160.79 ± 15.16 and diastolic blood pressure was 104.37 ± 13.653 at admission.
The mean urinary protein excretion in 24 hours was 1067.8 ± 78 mg/dl (range, 200 mg/dl to 3000 mg/dl). The mean P/c ratio was 0.338 ± 0.15 (range 0.143 to 0.72). The correlation coefficient for the P/C ratio against the 24 hour urine protein excretion was 0.71 (R2 = 0.71).
The predictor model of regression equation was Y = −269.19 + 3715.15 X, (P < 0.0001) where X = spot protein creatinine ratio and Y = 24 hour urine protein.
Figure 1 shows the relationship between 24 hours protein excretion and spot protein-creatinine (P/C) ratio. The curve indicates very good linear relationship between the two variables which is also indicated by strong correlation coefficient (r = 0.71, P = 0.0001).
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