Spot Urinary Albumin–Creatinine Ratio in Prediction of Pre-eclampsia: A Prospective Study

Abstract

Background: Pre-eclampsia is a multisystem disorder with two-stage disease pathology where abnormal placentation precedes the endothelial dysfunction which ultimately leads to the systemic inflammatory response. Endothelial dysfunction is one of the hallmark pathologies of preeclampsia, microalbuminuria is the measure of the same and could be used as a marker for predicting pre-eclampsia in early gestation. This study has been carried out to predict pre-eclampsia among low-risk pregnant women with the use of spot urine albumin-creatinine ratio (ACR) and to derive at a definite cut-off value of spot urine ACR. Materials and methods: This prospective study was done in ESIC Medical College & PGIMSR, Chennai, Tamil Nadu, India, for a period of 12 months. Low-risk singleton pregnant women between 16 and 20 weeks of gestational age who satisfied the inclusion criteria were considered. Participants who tested negative for urine albumin by urine dipstick method were subjected to a spot urine ACR test. Urine albumin was measured by the immunoturbidimetric method and urine creatinine by Jaffe's kinetic method. Urine albumin is expressed as mg/dL, urine creatinine as gm/dL, and ACR as mg/gm. All the participants were followed up to delivery. The primary outcome measure was pre-eclampsia, secondary outcome measures were gestational hypertension (GHTN), gestational diabetes mellitus (GDM), intrauterine growth restriction (IUGR), and a cut-off value of urine spot ACR in the prediction of pre-eclampsia was calculated by receiver operative curve (ROC) analysis. Results: Among 164 participants, the proportion of pregnant women affected with pre-eclampsia was 3.04%. The optimum value of ACR in predicting pre-eclampsia obtained was 25.89 mg/gm by applying the ROC curve. It also derived 80% sensitivity and 87% specificity with a positive predictive value (PPV) of 16% and a negative predictive value (NPV) of 99%. Conclusion:The ACR test is widely available with easy interpretation and also convenient for pregnant women. Spot urine ACR value of more than 25.89 mg/gm in asymptomatic pregnant women when measured between 16 and 20 weeks of gestation can predict the development of pre-eclampsia with the sensitivity and specificity of 80 and 87%, respectively. The higher NPV value of 99% of spot urine ACR ratio may help in accurately diagnosing true negatives. However, additional prospective studies with higher sample size and cost-benefit analysis of the test are recommended to confirm these findings before routinely using urine spot ACR as a predictive marker.