First-trimester prediction of pre-eclampsia: external validity of algorithms in a prospectively enrolled cohort

Revisiting the discriminatory accuracy of traditional risk factors in preeclampsia screening

BACKGROUND

Preeclampsia (PE) is associated with a high risk of perinatal morbidity and mortality. However, there is no consensus in the definition of high-risk women.

AIM

To question current definition of high PE risk and propose a definition that considers individual heterogeneity to improves risk classification.

METHODS

A stratified analysis by parity was conducted using the Swedish Birth Register between 2002-2010 including 626.600 pregnancies. The discriminatory accuracy (DA) of traditional definitions of high-risk women was compared with a new definition based on 1) specific combinations of individual variables and 2) a centile cut-off of the probability of PE predicted by a multiple logistic regression model.

RESULTS

None of the classical risk-factors alone reached an acceptable DA. In multiparous, any combination of a risk-factor with previous PE or HBP reached a +LR>10. The combination of obesity and multiple pregnancy reached a good DA particularly in the presence of previous preeclampsia (positive likelihood ratio (LR+) = 26.5 or chronic hypertension (HBP) LR+ = 40.5. In primiparous, a LR+>15 was observed in multiple pregnancies with the simultaneous presence of obesity and diabetes mellitus or with HBP. Predicted probabilities above 97 centile in multiparous and 99 centile in primiparous provided high (LR+ = 12.5), and moderate (LR+ = 5.85), respectively. No one risk factor alone or in combination provided a LR- sufficiently low to rule-out the disease.

CONCLUSIONS

In preeclampsia prediction the combination of specific risk factors provided a better discriminatory accuracy than traditional single risk approach. Our results contribute to a more personalized risk estimation of preeclampsia.

Validation of a first-trimester screening model for pre-eclampsia in an unselected population

OBJECTIVE

To validate the performance of a previously constructed first-trimester predictive model for pre-eclampsia (PE) in routine care of an unselected population.

METHODS

A validation cohort of 4621 consecutive women attending their routine first-trimester ultrasound examination was used to test a prediction model for PE that had been developed previously in 5170 women. The prediction model included maternal factors, uterine artery Doppler, blood pressure and pregnancy-associated plasma protein-A. Model performance was evaluated using receiver-operating characteristics (ROC) curve analysis and ROC curves from both cohorts were compared unpaired.

RESULTS

Among the 4203 women included in the final analysis, 169 (4.0%) developed PE, including 141 (3.4%) cases of late-onset PE and 28 (0.7%) cases of early-onset PE. For early-onset PE, the model showed an area under the ROC curve of 0.94 (95% CI, 0.88-0.99), which did not differ significantly (P = 0.37) from that obtained in the construction cohort (0.88 (95% CI, 0.78-0.99)). For late-onset PE, the final model showed an area under the ROC curve of 0.72 (95% CI, 0.66-0.77), which did not differ significantly (P = 0.49) from that obtained in the construction cohort (0.75 (95% CI, 0.67-0.82)).

CONCLUSION

The prediction model for PE achieved a similar performance to that obtained in the construction cohort when tested on a subsequent cohort of women, confirming its validity as a predictive model for PE. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Should we recommend universal aspirin for all pregnant women?

Low-dose aspirin has been demonstrated to reduce the incidence of preeclampsia and fetal growth restriction in at-risk populations. Its role in low-risk populations is as yet unknown. Novel preeclampsia screening tests are emerging that can predict the risk of the development of preeclampsia from as early as 11 weeks of gestation. It may be more efficacious, acceptable, and cost-effective to prescribe low-dose aspirin to all pregnant women from the first trimester as opposed to performing a screening test in the first instance. There is variation in opinion: the American College of Obstetricians and Gynecologists suggests the use of aspirin only in women who are at risk of preeclampsia, based on patient history; the National Institute for Health and Clinical Excellence, UK, and the US Preventative Services Task Force recommend the use of low-dose aspirin if there is 1 major or 2 moderate risk factors. This point-counterpoint discussion shall address (1) controversies regarding the real impact of low-dose aspirin; (2) controversies in the actual guidelines among the different national societies; (3) controversies regarding emerging preeclampsia screening tests in terms of cost-effectiveness and efficacy, and (4) points in favor of the provision of universal vs screened-positive women.

Bedside diagnosis of two major clinical phenotypes of hypertensive disorders of pregnancy

OBJECTIVE

To investigate the hypothesis that fetal abdominal circumference (AC) and uterine artery (UtA) Doppler pulsatility index (PI) could be used to select two homogeneous subgroups of women affected by hypertensive disorders of pregnancy (HDP), characterized by the coexistence of maternal hypertension with and without intrauterine growth restriction (IUGR).

METHODS

This was a multicenter retrospective study of cases affected by HDP in whom fetal AC and UtA-PI had been measured at admission to fetomaternal medicine units. Maternal characteristics, pregnancy complications and outcome were recorded. These data allowed us to model the characteristics of fetal growth in cases affected by HDP, and to design composite indicators of risk factors for maternal metabolic syndrome and of severity for maternal functional organ damage.

RESULTS

Measurements of fetal AC and UtA-PI allowed us to define a group of HDP cases with appropriate-for-gestational-age (AGA) fetuses (HDP-AGA), diagnosed by normal fetal AC and UtA-PI (n = 205), and a group of HDP cases with IUGR fetuses (HDP-IUGR), diagnosed by fetal AC < 5(th) centile and UtA-PI > 95(th) centile (n = 124). Curves fitted to the birth weights of these two groups were significantly different, but gestational age at admission for HDP (< 34 or ≥ 34 weeks) did not show an independent association with birth weight. When birth weight was expressed as a Z-score with respect to local reference charts, the average corresponded to the 6(th) and 48(th) centiles, respectively. The occurrence of HDP-AGA (as compared with HDP-IUGR) was significantly associated with risk factors for maternal metabolic syndrome (odds ratio, 2.79 (95% CI, 1.57-4.97)), independent of gestational age. The same risk factors yielded non-significant odds ratios for the development of late-onset (vs early-onset) HDP. Women with HDP-IUGR had worse clinical outcomes.

CONCLUSIONS

This study provides new information based on simple prenatal bedside examinations that might help to differentiate HDP-IUGR from HDP-AGA fetuses. These groups are associated with different fetal growth patterns and risk factors, independent of gestational age at onset of the disease. Copyright © 2015 ISUOG. Published by John Wiley & Sons Ltd.

An open-label randomized-controlled trial of low dose aspirin with an early screening test for pre-eclampsia and growth restriction (TEST): Trial protocol

OBJECTIVE

Pre-eclampsia remains a worldwide cause of maternal and perinatal morbidity and mortality. Low dose aspirin (LDA) can reduce the occurrence of pre-eclampsia in women with identifiable risk factors. Emerging screening tests can determine the maternal risk of developing placental disease, such as pre-eclampsia from the first trimester of pregnancy. The aim of this study is to determine if it is more beneficial in terms of efficacy and acceptability to routinely prescribe LDA to nulliparous low-risk women compared to test indicated LDA on the basis of a positive screening test for placental disease.

METHODS

We propose a three armed multi-center open-labeled randomized control trial of; (i) routine LDA, (ii) no aspirin, and (iii) LDA on the basis of a positive first trimester pre-eclampsia screening test. LDA (75mg once daily) shall be given from the first trimester until 36-week gestation. The primary outcome measures include; (i) the proportion of eligible women that agree to participate (acceptability), (ii) compliance with study protocol (acceptability and feasibility), (iii) the proportion of women in whom it is possible to obtain first trimester trans-abdominal uterine artery Doppler examination (feasibility) and (iv) the proportion of women with a completed screening test that are issued the screening result within one week of having the test performed (feasibility).

CONCLUSION

This will be the first clinical trial to determine the efficacy and acceptability in low-risk women of taking routine LDA versus no aspirin versus LDA based on a positive first trimester screening test for the prevention of placental disease.

First trimester screening for pre-eclampsia

The commercial availability of tests in the first trimester of pregnancy that predict the later development of pre-eclampsia has prompted considerable debate regarding their clinical utility and the degree to which they fulfil the longstanding principles of screening. Such tests have been shown to achieve detection rates for early pre-eclampsia (requiring delivery prior to 34 weeks) of over 90%, for a false positive rate of 10%. However, their capacity to predict later onset pre-eclampsia, which accounts for the bulk of the disease burden, is much more limited. The relatively few studies validating the performance of these tests in different populations have demonstrated significant variations in performance. Moreover, prospective research confirming that the administration of aspirin to those screened to be high risk reduces the incidence of pre-eclampsia is yet to be completed, and there may be harms in restricting aspirin therapy to this group, given its broader beneficial effect. In light of these limitations, further development of these tests is recommended prior to their introduction to clinical practice.

Angiogenic balance (sFlt-1/PlGF) and preeclampsia

Preeclampsia is a hypertensive disorder of pregnancy associated with important maternal and perinatal mortality and morbidity. Although symptomatic management has improved, there is currently no curative treatment, and only childbirth and delivery of the placenta, usually prematurely, alleviate the mother's symptoms. Placental insufficiency plays a central role in the pathophysiology of preeclampsia. Abnormal placentation during the first trimester leads to defective remodeling of the uterine vascularization. This results progressively in placental hypoperfusion, which induces trophoblast dysfunction and the release in maternal circulation of trophoblastic factors leading to an excessive inflammatory response, endothelial dysfunction and glomerular damage. Among these factors, the most important is sFlt-1, which is a soluble form of the VEGF and PlGF receptor. sFlt-1 binds to free VEGF and PlGF in the maternal circulation, thus reducing their bioavailability for their membrane receptor. The result is inhibition of the effects of VEGF and PlGF on maternal endothelial cells and podocytes. The sFlt-1/PlGF ratio reflects the circulating angiogenic balance and is correlated with severity of the disease.

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.

Angiogenesis-Related Biomarkers (sFlt-1/PLGF) in the Prediction and Diagnosis of Placental Dysfunction: An Approach for Clinical Integration

Placental dysfunction is involved in a group of obstetrical conditions including preeclampsia, intrauterine growth restriction, and placental abruption. Their timely and accurate recognition is often a challenge since diagnostic criteria are still based on nonspecific signs and symptoms. The discovering of the role of angiogenic-related factors (sFlt-1/PlGF) in the underlying pathophysiology of placental dysfunction, taking into account that angiogenesis-related biomarkers are not specific to any particular placental insufficiency-related disease, has marked an important step for improving their early diagnosis and prognosis assessment. However, sFlt-1/PlGF has not been yet established as a part of most guidelines. We will review the current evidence on the clinical utility of sFlt-1/PlGF and propose a new protocol for its clinical integration.

First-trimester uterine artery Doppler analysis in the prediction of later pregnancy complications

Uterine artery Doppler waveform analysis has been extensively studied in the second trimester of pregnancy as a predictive marker for the later development of preeclampsia and fetal growth restriction. The use of Doppler interrogation of this vessel in the first trimester has gained momentum in recent years. Various measurement techniques and impedance indices have been used to evaluate the relationship between uterine artery Doppler velocimetry and adverse pregnancy outcomes. Overall, first-trimester Doppler interrogation of the uterine artery performs better in the prediction of early-onset than late-onset preeclampsia. As an isolated marker of future disease, its sensitivity in predicting preeclampsia and fetal growth restriction in low risk pregnant women is moderate, at 40–70%. Multiparametric predictive models, combining first-trimester uterine artery pulsatility index with maternal characteristics and biochemical markers, can achieve a detection rate for early-onset preeclampsia of over 90%. The ideal combination of these tests and validation of them in various patient populations will be the focus of future research.

External validity of first-trimester algorithms in the prediction of pre-eclampsia disease severity

OBJECTIVE

To compare disease features in women with pre-eclampsia between those who are correctly identified (true positive) and those who are missed (false negative) when applying first-trimester prediction algorithms for pre-eclampsia to a prospectively enrolled population.

METHOD

Six first-trimester early (requiring delivery < 34 weeks' gestation) pre-eclampsia algorithms were applied to a prospective cohort of singleton pregnancies enrolled at first-trimester screening. Maternal outcomes, neonatal outcomes and severity parameters for pre-eclampsia were compared between true-positive and false-negative predictions.

RESULTS

Twenty of 2446 (0.8%) women developed early pre-eclampsia, with 65% of these developing severe features and 20% HELLP syndrome. At enrollment, true-positive cases were more likely to be African-American and chronically hypertensive, while false-negative cases were more likely to be Caucasian. At delivery, true-positive cases were more likely to have pre-eclampsia superimposed on hypertension, severely elevated blood pressure and creatinine level > 1.1 mg/dL. False-negative cases were more likely to have HELLP syndrome (all P < 0.05).

CONCLUSION

In an urban population with a high prevalence of chronic hypertension, patients who are correctly identified by first-trimester screening models are more likely to develop pre-eclampsia superimposed on chronic hypertension with severely elevated blood pressure and evidence of renal failure. In contrast, patients who are missed by these algorithms are more likely to have HELLP syndrome. Further research is needed to confirm these findings and the algorithm adjustments that may be necessary to better predict pre-eclampsia phenotypes.