The prediction of preeclampsia: reassessment of clinical value of increased plasma levels of fibronectin

Ischemic placental syndrome--prediction and new disease monitoring

The last decade has seen an improved understanding of the cause of the development of pathologies such as gestational hypertension, preeclampsia, intrauterine growth restriction, intrauterine fetal death or placental abruption. Nowadays, we know that most conditions within this group share the same pathogenesis, the cause of which is placental ischemia. The following review is an attempt to propose a new method for prediction, diagnosis and--above all--appropriate monitoring of pregnant women and fetuses developing the ischemic placental syndrome with the use of tests that are new but yet widely available in clinical diagnosis. They are closely related to the condition's pathogenesis, therefore their elevated levels may predate clinical symptoms, and--most importantly--they correlate with syndrome aggravation and the occurrence of complications. Perhaps, the new look will allow us to improve perinatal results by reducing mortality and severe complications in pregnant women and fetal deaths resulting from sudden intrauterine fetal death or placental abruption.

Prediction of pre-eclampsia in early pregnancy

Pre-eclampsia is a multisystem disorder of pregnancy, usually characterized by the appearance of high blood pressure and the excretion of protein in the urine of a previously healthy woman. Symptoms and signs vary in intensity from woman to woman; from a borderline rise in blood pressure, to convulsions (eclampsia), stroke and death. The disease remits following removal of the placenta and so the mainstay of current treatment is timely delivery. A pathophysiological framework of the disease has been established, beginning with failures in placental development, inducing oxidative stress and release of compounds that lead to endothelial activation, vasoconstriction and glomerular endotheliosis. A combination of epidemiological, biophysical and biochemical tests now allow most patients at-risk to be identified by midpregnancy, whilst minimizing false-positive prediction. It is hoped that earlier classification of patients at-risk of the disease, on the basis of pathophysiological changes, will enable specific therapies to be developed targeting these changes.

Role of anion gap and different electrolytes in hypertension during pregnancy (preeclampsia)

The present study was designed to determine the changes in serum sodium, anion gap, different antioxidants and free radicals in preeclamptic patients and control subjects. Serum sodium, chloride, bicarbonate, calcium, potassium and magnesium were estimated and anion gap was determined in 100 proteinuric hypertensive and 100 normotensive pregnant women. Mean serum sodium, chloride and bicarbonate level (133.26 +/- 13.1, 104.97 +/- 11.37, and 22.01 +/- 4.66 mEq/l, respectively) were significantly higher in proteinuric hypertensive women as compared to controls (125.85 +/- 10.4, 101.90 +/- 6.3, 19.34 +/- 3.21 mEq/l, respectively) whereas anion gap level (6.28 +/- 16.147) was nonsignificantly higher in proteinuric hypertensive as compared to normotensive (4.61 +/- 11.84). Total serum sodium concentration increases in preeclamptic subjects, the exact distribution of serum sodium in various compartments of the body are not clear and correlation of serum sodium and anion gap with proteinuria is also not known. The levels of different antioxidants were decreased in preeclamptic patients as compared to the controls while the level of free radicals elevated in preeclamptic subjects as compared to controls. In our study, anion gap level was found to be rather non-significantly higher in proteinuric hypertensive women as compared to normotensive women.

Prediction and prevention of preeclampsia and IUGR

Preeclampsia, being one of the leading causes of maternal and perinatal morbidity and mortality, has been the subject of extensive research since its description. Preeclampsia has been called the disease of theories due to the enigma surrounding its exact pathophysiology. Despite the absence of treatment that reverses the disease process once started, screening for preeclampsia and intrauterine growth restriction (IUGR) has been a major clinical and research issue since the disease was first reported. This review evaluates the current evidence for prediction and prevention of preeclampsia and IUGR using clinical tests, maternal serum markers, and uterine artery Doppler screening. In addition, we critically evaluate the evidence regarding the different therapeutic strategies for the prevention of preeclampsia and IUGR and the latest clinical recommendations for their use.

Prediction of preeclampsia with maternal mid-trimester placental growth factor, activin A, fibronectin and uterine artery Doppler velocimetry

OBJECTIVE

To assess whether alterations in the serum levels of placental growth factor, activin A and fibronectin could be detected in patients before they become preeclamptic. And to evaluate and compare the clinical utility of these markers and uterine artery Doppler velocimetry in predicting preeclampsia.

METHODS

One hundred and twenty-two normotensive women were prospectively included in the study. Peripheral venous blood samples were obtained and Doppler examination of the uterine arteries was performed between 21 and 26 weeks' gestation. Serum levels of placental growth factor, activin A and fibronectin were measured by enzyme-linked immunoassay and radial immundiffusion technic.

RESULTS

Mid-trimester maternal serum activin A and fibronectin levels and average S/D ratios were significantly higher whereas placental growth factor levels were significantly lower in women who subsequently developed preeclampsia than remained normotensive (p<0.001). The best cut-off values for predicting preeclampsia of placental growth factor, activin A and fibronectin based on ROC curve analysis were 90 pg/ml, 14 ng/ml and 370 mg/l respectively. The areas under the curve equal to 0.993, 0.972, 0.872 and 0.813 for placental growth factor, activin A, fibronectin and uterine artery Doppler respectively were determined for the prediction of preeclampsia.

CONCLUSION

Placental growth factor, activin A, fibronectin and uterine artery Doppler are all potentially useful as predictors of preeclampsia. Maternal serum midtrimester PGF has the highest predictive value and activin A with a compatible accuracy for early identification of preeclampsia.

World Health Organization Systematic Review of Screening Tests for Preeclampsia

OBJECTIVE

We sought to assess the usefulness of clinical, biophysical, and biochemical tests in the prediction of preeclampsia.

DATA SOURCES

The sources of data we used to conduct this review included the computerized databases MEDLINE (1966 to February 2003), EMBASE, Popline, CINAHL, and LILACS plus reference lists, conference proceedings, textbooks, and contact with experts.

METHODS OF STUDY SELECTION

All cohort or cross-sectional studies reporting data on the relationship between a predictive test that was performed during pregnancy and the development of preeclampsia were eligible for inclusion, whereas case-control studies were excluded. Eighty-seven (211,369 women) of 7,191 potentially relevant articles met inclusion criteria. We evaluated the methodologic quality for each included study.

TABULATION, INTEGRATION, AND RESULTS

Using a standardized protocol, one reviewer selected and extracted data on study characteristics, quality, and accuracy. Data abstracted from each study were arranged in 2 x 2 tables to construct receiver operating characteristics plots (sensitivity against 1 - specificity) and pooled to produce summary likelihood ratios for positive and negative tests results. Moderate predictive accuracy of anticardiolipin antibodies, the presence of bilateral diastolic notches during Doppler ultrasonography, and urinary kallikrein were found in women at low risk of developing preeclampsia. Nevertheless, because the pretest probability of preeclampsia with a positive result was but minimally increased, the clinical use of these tests is limited. Other ultrasonography characteristics and the measurement of fetal and placental peptides showed low predictive accuracy. In populations that were deemed at high risk for preeclampsia, the use of Doppler ultrasonography had low predictive accuracy. No definitive conclusions were possible in the case of many other tests, because the number of studies that met the minimal inclusion criteria was limited.

CONCLUSION

As of 2004, there is no clinically useful screening test to predict the development of preeclampsia. Further prospective, longitudinal studies are needed.

Prediction of preeclampsia: can it be achieved?

In this review, the various biochemical tests that have been proposed for the prediction of preeclampsia are described and evaluated. Placenta hormone markers do not predict future disease. They denounce the early placental changes that are part of the evolving disease and only predict the imminent of preeclamptic syndrome. This explains why tests are better predictors when preeclampsia supervenes shortly, and why screening in the first trimester is unlikely to work as well as in the second trimester. The use of multiple markers in the screening should reflect different aspects of the disease process and could increase the specificity and sensitivity of the screening and work on different etiologic factors. The possible use of second-trimester biochemical screening to predict the risk of preeclampsia remains to be investigated in the high-risk population.

TARGET AUDIENCE

Obstetricians & Gynecologists, Family Physicians

LEARNING OBJECTIVES

After completion of this article, the reader should be able to list the various theories on the etiology of preeclampsia, to relate the various risk factors for the development of preeclampsia, and to describe the various screening tests for preeclampsia.

Maternal erythrocyte malondialdehyde level in preeclampsia prediction: a longitudinal study

We aimed to determine the value of maternal erythrocyte malondialdehyde levels in the prediction of preeclampsia. 110 healthy women were included in this prospective study. Maternal erythrocyte malondialdehyde levels were measured at each trimester of pregnancy (10-14, 20-25 and 30-35 gestational weeks). On follow-up, patients were assigned to two groups as normotensive women and preeclamptic patients. Preeclampsia had developed in eight (8.9%) of the 90 pregnant women who completed the study. Preeclamptic patients were diagnosed between 36 and 39 gestational weeks (36.8 +/- 1.0 weeks). Malondialdehyde levels of preeclamptic patients increased significantly in the third trimester (p < 0.05), while there was no difference between values of malondialdehyde in the first and second trimester. Malondialdehyde levels were significantly higher in the patients who developed preeclampsia than in those who did not in the third trimester (p < 0.05). With the use of the receiver operating characteristics (ROC) 35.98 nmol malondialdehyde/gm hemoglobin was found to be a cut-off value predictive for the development of preeclampsia in the third trimester. However, cut-off values in the first and second trimesters could not be found. The sensitivity, specificity, positive and negative predictive values were 89, 75, 29 and 98%, respectively. Preeclampsia risk was found to increase nearly 24 times in values above 35.98 nmol malondialdehyde/ gm hemoglobin. Our results showed that maternal erythrocyte malondialdehyde could predict patients within a few weeks prior to onset of clinical symptoms of preeclampsia in the third trimester. There is no evidence of enhanced early lipid peroxidation in pregnancies with late onset preeclampsia.

Maternal plasma cellular fibronectin concentrations in normal and preeclamptic pregnancies: a longitudinal study for early prediction of preeclampsia

OBJECTIVE

The purpose of this study was to examine cellular fibronectin levels throughout normotensive and preeclamptic pregnancies and to analyze its predictive value for the detection of preeclampsia within the second trimester of pregnancy.

STUDY DESIGN

Blood samples were collected at 4-week intervals from 378 healthy, nulliparous women who were recruited before 16 weeks of gestation. Preeclampsia developed in 26 patients; 52 normotensive control subjects were matched from the same cohort. Plasma samples were assayed for ED-B fibronectin by enzyme-linked immunosorbent assay. Trends were compared between groups. Predictive values were determined with the use of second trimester assessments.

RESULTS

In both groups, fibronectin levels rose as pregnancy advanced, but in women with preeclampsia, this increase was significantly higher (94.5% vs 31.8%; P =.006). Throughout pregnancy, patients with preeclampsia exhibited significantly higher fibronectin levels than did control subjects. As early as 9 to 12 weeks of gestation, a difference was established (preeclampsia, 3.72 +/- 0.21; control, 2.94 +/- 0.22 microg/mL [mean +/- SEM]; P =.008). The best cutoff point and time interval to calculate predictive values were 3.8 microg/mL and 22 to 26 weeks of gestation, respectively. Sensitivity, specificity, and positive and negative predictive values were 73%, 87%, 29%, and 98%, respectively; the odds ratio was 16.1 (95% CI, 8.6-30.2).

CONCLUSION

In women in whom clinical preeclampsia developed, endothelial damage seemed to be present since early gestation. Cellular fibronectin levels of >or=3.8 microg/mL within 22 to 26 weeks of gestation may help in the early detection of preeclampsia in healthy nulliparous women.