Use of a random urinary protein-to-creatinine ratio for the diagnosis of significant proteinuria during pregnancy.

OBJECTIVE: The purpose of this study was to evaluate whether a random urinary protein-to-creatinine ratio is a clinically useful predictor of significant proteinuria (300 mg/24 hour).

STUDY DESIGN: The medical records of 138 women who completed both a random urinary protein-to-creatinine ratio and a 24-hour urine collection for the evaluation of preeclampsia were reviewed. Urine samples for the random protein-to-creatinine ratio were collected before the 24-hour urine collection. With the use of a protein level of at least 300 mg in the 24-hour urine sample as the gold standard, the sensitivity and specificity of the random protein-to-creatinine ratio for the diagnosis of significant proteinuria were determined with a range of cutoffs.

RESULTS: Fifty percent of the study population had significant proteinuria. The data suggest that a cutoff below 0.14 ruled out significant proteinuria. The best cutoff of > or = 0.19 yields a sensitivity of 90% and a specificity of 70%. All of the false-negative test results had 24-hour urine protein levels below 400 mg; 13 of the 21 false-positive results had levels that ranged from 250 to 300 mg.

CONCLUSION: The random urinary protein-to-creatinine ratio is strongly associated with the 24-hour total protein excretion. A level below 0.14 can rule out significant proteinuria. A best cutoff of > or = 0.19 is a good predictor of significant proteinuria. With further study, the random urinary protein-to-creatinine ratio could replace the 24-hour urine collection as a simpler, faster, more useful method for the diagnosis of significant proteinuria.