A comparison of the inactive urinary kallikrein:creatinine ratio and the angiotensin sensitivity test for the prediction of pre‐eclampsia

OBJECTIVE: To determine the relation between the inactive urinary kallikrein: creatinine ratio (IUK:Cr) and the angiotensin sensitivity test (AST) at 28 weeks of gestation and to assess each as a screening test for pre-eclampsia. DESIGN: Prospective interventional study. SUBJECTS: Four hundred and fifty-nine normotensive nulliparous women recruited from hospital antenatal clinics. SETTING: John Radcliffe Maternity Hospital, Oxford, and Queen Charlotte's and Chelsea Hospital, London. INTERVENTIONS: A urine sample for IUK:Cr measurement was provided before performing the AST at 28 weeks of gestation. Those women who demonstrated increased sensitivity to angiotensin II were entered into a randomised placebo controlled trial of low dose aspirin for the prevention of pre-eclampsia (CLASP). MAIN OUTCOME MEASURES: The development of pre-eclampsia. RESULTS: The IUK:Cr ratio was significantly lower in those women who showed increased sensitivity to angiotensin II (P < 0.0001 Student's t test). The sensitivity and specificity for detecting pre-eclampsia were, respectively, 22% and 85% for the AST and 67% and 75% for the IUK:Cr. Low-dose aspirin (60 mg) had no effect on the pregnancy outcome. CONCLUSION: There appears to be some relation between the IUK:Cr and AST tests in pregnancy. However, in this population, the IUK:Cr ratio was a better screening test for pre-eclampsia than the AST, but overall neither test was a powerful predictor for the syndrome.