Objectives: To determine the correlation between the protein/creatinine ratio and 24-h proteinuria; to estimate the sensitivity and specificity of this ratio for the diagnosis of significant proteinuria; to establish its cutoff point with the best predictive value for the diagnosis of significant proteinuria in patients with systemic arterial hypertension.
Study design: A cross-sectional study of 47 hypertensive patients who had been pregnant for 20 weeks or more seen at the Maternity of the University Hospital of Porto Alegre. The studied factor was the protein/creatinine ratio measured in a single random urine sample and the outcome was protein determination in 24-h urine. The level of significance was set at 0.05.
Results: The correlation coefficient between the protein/creatinine ratio and 24-h proteinuria was 0.94 when urine was properly collected. A receiver-operator characteristic curve was constructed to determine the sensitivity and specificity of the ratio for the diagnosis of significant proteinuria (> or = 300 mg in 24 h). Specificity and predictive positive value were 100% for a ratio > or = 0.8. The best values for sensitivity, specificity, positive predictive value, and negative predictive value in the diagnosis of proteinuria > or = 300 mg in 24 h were obtained when the protein/creatinine ratio was 0.5 (0.96, 0.96, 0.96, and 0.96, respectively).
Conclusion: The protein/creatinine ratio measured in a single urine sample taken at random from hypertensive pregnant women showed good sensitivity and specificity for the diagnosis of 24-h proteinuria > or = 300 mg and was strongly correlated with 24-h proteinuria. A ratio of 0.5 mg/mg is predictive of significant proteinuria and can be used for the diagnosis and follow-up of hypertensive pregnant women.