Survey of predictive value of 4-hour urine collection for diagnosis of proteinuria in preeclampsia

Measuring the 24-hour urine protein ≥300 mg is the standard threshold value for diagnosis of preeclampsia. This study was intended to determine if a patient’s 4-hour urine protein correlate with the 24-hour value for diagnosis of preeclampsia. This was a cross sectional study performed on 84 women with suspected preeclampsia due to positive urinary test strip with minimum protein content of 1+ and BP ≥140/90 at Al-zahra Educational Hospital in Rasht (Iran) from May 2007 to January 2008. Urine samples were collected within 24 hours in successive periods: The first 4-hour and the next 20-hours urine, in separate containers. The protein contents of 4-hour and 24-hour urine samples were calculated. Data were analyzed by intra-class correlation coefficient, and Receiver Operating Characteristic (ROC) curve. The ROC curve showed the cut-off point of 55.5 for 4-hour urine protein. The correlation between 4- and 24-hour urine protein excretions identified that most women (about 85.1%) with protein excretion rate of 300 mg/24h or more (with preeclampsia) had the same amount of protein of 55.5 or more in their 4-hour urine excretion (p<0.001). Also, most of them (about 83.7%) with a total urinary protein excretion of less than 300 mg/24h (no preeclampsia) had a protein excretion rate of less than 55.5 mg/4h. This study showed 4-hour protein collection can be used as acceptable substitute for assessing the protein content of 24-hour urine samples as a more convenient, faster, and cheaper method for diagnosis of preeclampsia and the cut-off point for 4-hour urine protein is 55.5 mg.