Relationship between urinary albumin and albumin/creatinine ratio during normal pregnancy and pre-eclampsia

Pre-eclampsia is a serious complication of pregnancy and it is important to detect the condition as early as possible. Albuminuria is an important symptom of pre-eclampsia and repeated urine analyses to screen for the condition are part of the standard antenatal care. The purpose of this study was to investigate whether measurement of the urine albumin/creatinine ratio in spot samples could be a complement to the dipstick method and could reduce the need for 24-h urine collections. Urine samples were collected for 24 h in weeks 12, 24 and 36 of pregnancy from both normotensive women and women who developed hypertension or who had pregnancy-induced hypertension (PIH) when they entered the study. The 24-h albumin excretion was significantly correlated to the albumin/creatinine ratio in all measurements (Pearson correlation coefficient). In week 12, the values were: n = 44, r = 0.964, p < 0.001 (normotensive group) and in the PIH group: n = 8, r = 0.789, p < 0.05. In week 24, the correlation values were r = 1.0 and p < 0.001 in both the normotensive group (n = 41) and in the PIH group (n = 11). In week 36 the correlation values were r = 0.791 and p < 0.001 in the normotensive group (n = 39) and r = 1.0 and p < 0.001 in the PIH group (n = 16). Microalbuminuria was defined as urine albumin excretion higher than 30 mg/24 h and this corresponded to an albumin/creatinine ratio of 2.9. Microalbuminuria was found in three persons in the PIH group and in two persons in the normotensive group. Overt albuminuria (> 300 mg/24 h) was found in one of the 46 normotensive women (2%) and in 3 of the 19 PIH women (16%). In all these women the high albumin values had been detected by using the albumin/creatinine ratio method. In conclusion, it has been found that the albumin excretion in urine correlates significantly to the albumin/creatinine ratio during pregnancy. The urinary albumin/creatinine ratio appears to be a good alternative to the dipstick method and to 24-h urine collections.