Objectives: We developed a simplified method using a relatively small volume of blood for the determination of platelet angiotensin II receptors by saturation analysis and we evaluated its performance for the prediction of preeclampsia.
Design and methods: A platelet suspension with minimal contamination by leukocytes and erythrocytes is obtained by centrifugation and washing. The platelet concentrate is incubated in a multi-well plate with increasing concentration of radiolabelled angiotensin II in the presence or absence of an excess of unlabelled angiotensin II. Bound and free fractions are separated using an oil mixture. Maximum binding is determined by Scatchard plot. This method was compared with a previously reported method. Our method was prospectively evaluated in 801 women attending our institution for routine prenatal care. A specimen was obtained at each trimester of pregnancy whenever possible. Diagnosis of preeclampsia was done postnatally by an experienced obstetrician.
Results: The method showed acceptable correlation with a previously published method although a proportional bias of 2.1 was observed between the two methods. No differences in mean maximum binding were observed between normal and affected pregnancies at either trimester. Even when the results were analyzed longitudinally, using the change in maximum binding between two trimesters for each patient, no significant increase could be documented in preeclamptic pregnancies.
Conclusions: Platelet angiotensin II receptor measurement is not a clinically useful marker for the prediction of preeclampsia.