Using 2-hour/6-hour Urine Protein Measurement as Substitute Diagnostic Methods for Evaluation of Pre-Eclampsia

Abstract

Objective: To determine whether the gold standard of 24-hour urine protein value in pre-eclampsia patient can be substituted with 2-hour or 6-hour urine protein values. Method: We conducted a cross sectional study on women with pre-eclampsia ( a positive urinary test strip for protein of at least 1+ and a BP140/90 mmHg. Urine samples were collected over 24 hours in subsequent periods: the first 2-hour and the next 6hour and remaining 16-hour urine , in separate containers . The correlation between both groups was determined by Pearson's correlation. Result: A total of 36 women were recurited in our study of which 26 had completed urine collection. A total of 16 had mild proteinuria, 2 had severe proteinuria and 8 had no proteinuria. Only 21 of 26 women had the measurements for 6-hour urine collection. There was significant correlation between the 6-hour or 2-hour with 24-hour urine protein. Conclusion: Total protein values of 6-hour and 2-hour samples, specially 2-hour urine samples, positively correlated with values of 24-hour samples in pre-eclampsia women and could be substituted for assessment of proteinuria instead of 24-hour urine collection in women with pre-eclampsia, as a simpler, faster and cheaper method for diagnosis of pre-eclampsia. Five to seven per cent of pregnant women are affected with pre-eclampsia, although the incidence of pre-eclampsia is different depending on the geographical location. One of the most common causes of the hospitalization and mortality of pregnant patients in hospitals is eclampsia [1]. According to the national health statistics center, pregnancy-related hypertension is considered the most common serious and dangerous factor for the mother and her fetus [2]. The minimum diagnostic criteria for pre-eclampsia are hypertension (BP 140/90 mmHg) after 20 weeks of gestation and mild proteinuria; more severe forms of pre-eclampsia are characterized by BP 160/110 mmHg and proteinuria >2g/24h or 2+dipstick. Proteinuria is an important sign of pre-eclampsia and Chesly (1985) rightly concluded that the diagnosis of pre-eclampsia is under question in the absence of proteinuria [1]. Repeated Urine Analysis for screening proteinuria is part of standard ante-natal care. These urine analyses are performed on random spot urine specimens using a test strip assay (dipstick) which for pregnant women is more acceptable than 24hour urine collection. However, if a dipstick is 2+ or more in the absence of bacteria, the next step is usually a 24hour urine collection for a quantitative measurement of albumin. If a 24-hour urine collection is not possible, a third option, a morning urine sample (semi-quantitative test), is recommended. These recommendations are based on the circadian rhythm in urine albumin excretion [3]. However, for pregnant women, particularly if hospitalized, the circadian variations in albumin excretion are more narrow or even absent, and therefore a shorter urine collection period is possible[4]. When pre-eclampsia is associated with persistent proteinuria, protein excretion is monitored by subsequent 24Using 2-hour/6-hour Urine Protein Measurement as Substitute Diagnostic Methods for Evaluation of PreEclampsia 2 of 6 hour urine sample collections. This kind of monitoring can evaluate increases in proteinuria that show the progression of pre-eclampsia and reflect the severeity of nephropathy leading to pre-term labor [3]. The 24hour urine collection is the gold standard diagnostic method for significant proteinuria in hospitals [5], but it is usually considered difficult and costly and sometimes leads to incomplete collection of urine. In addition, it could delay the diagnosis. This delay in diagnosis of pre-eclampsia and its severity may result in unnecessary hospitalization and an economic burden for patients. Researchers have suggested faster methods for detection of proteinuria, such using the protein-to-creatinine ratio, and random urinary samples, but these do not reveal the severity of pre-eclampsia as reliably as 24hour urine collection [6]. It appears that a dipstick is a poor predictive tool for measuring significant proteinuria. Two-thirds of reported cases having mild proteinuria or no proteinuria by dipstick showed significant proteinuria in 24-hour urine collection [7]. We designed this study to evaluate the correlation between 2and 6-hour proteinuria with 24-hour proteinuria and if possible to suggest 2and 6-hour-samples as a shorter, acceptable, more affordable substitute for 24-hour samples in the primary evaluation of pre-eclamptic patients.