Objective: To investigate the correlation between spot albuminuria to creatinine ratio (ACR) and 24 h urinary protein excretion in women with preeclampsia and determine the optimal cut-off values of spot ACR in mild preeclampsia and severe preeclampsia.
Methods: Twenty-eight women with mild preeclampsia and 22 with severe preeclampsia at Nanfang Hospital, Southern Medical University between October 2010 and June 2011 were recruited. Maternal serum cystatin, uric acid, urea nitrogen, creatinine and albumin levels were collected and analyzed. Twenty-four hours urinary protein excretion was measured with immunoturbidimetric assay and ACR with automatic analyzer DCA2000. The correlation between ACR and 24 hours urinary protein excretion was explored. And the optimal cut-off values of the spot ACR for mild and severe preeclampsia were determined with receiver operating characteristic curve.
Results: (1) Maternal serum biochemical parameters: uric acid levels in mild and severe preeclampsia were (359 ± 114) µmol/L and (450 ± 132) µmol/L, while cystatin levels were (1.3 ± 0.3) mg/L and (1.6 ± 0.5) mg/L respectively. The differences were statistically significant (P < 0.05). Serum urea nitrogen, creatinine and albumin in mild preeclampsia were (3.6 ± 1.6) mmol/L, (52 ± 38) µmol/L and (33 ± 3) g/L, while in severe preeclampsia were (6.2 ± 3.1) mmol/L, (78 ± 59) µmol/L and (29 ± 6) g/L respectively. There were no statistical significant differences (P > 0.05). (2) Twenty-four hours urinary protein excretion and ACR: 24 hours urinary protein levels in mild and severe preeclampsia was (700 ± 160) mg and (4800 ± 2200) mg (P < 0.05). ACR in mild and severe preeclampsia was (72.7 ± 12.4) mg/mmol and (401 ± 245) mg/mmol respectively (P < 0.05). (3) There was a strong correlation between the spot ACR and 24 hours urine protein excretion (r = 0.938; P < 0.05). (4) The optimal spot ACR cut-off point for the diagnosis of preeclampsia: the optimal spot ACR cut-off point was 22.8 mg/mmol for 300 mg/24 hours of protein excretion in mild preeclampsia, the area under curve was 0.956, with a sensitivity, specificity of 82.4%, 99.4% respectively. And the optimal spot ACR cut-off point was 155.6 mol for 2000 mg/24 hours of protein excretion in severe preeclampsia, the area under curve was 0.956, with a sensitivity, specificity of 88.6%, 91.3% respectively.
Conclusions: Compared with 24 hours urinary protein excretion, the spot ACR may be a simple, convenient and accurate indicator of early diagnosis of preeclampsia. Spot ACR may be used as a replacement for 24 hours urine protein excretion in assessment of preeclampsia. The optimal spot ACR cut off points were 22.8 mg/mmol for mild preeclampsia and 155.6 mg/mmol for severe preeclampsia.