Diurnal variation in excretion of N-acetyl-beta-glucosaminidase during pregnancy: implications for the prediction of pre-eclampsia.

Significant differences in urinary excretion of N-acetyl-beta-glycosaminidase (NAG) were observed between nulliparous and multiparous patients and between fasted and nonfasted individuals. No significant difference was observed between patients with normal and those with abnormal glucose tolerance. Multiple regression analysis confirmed that the significant independent determinants of NAG/creatinine ratio were age, parity, gestation and fasting state. Significant diurnal variation in urinary NAG/Cr ratio was observed, the highest levels being recorded in early morning fasting specimens, falling in each postprandial specimen and beginning to rise again by midnight. The urinary NAG/Cr ratio is influenced by fasting, parity, gestation and age. More consistent results for prediction of pre-eclampsia are therefore likely to be obtained using fasting (early morning) urine specimens and adjusting cut-off criteria for the other factors.