soluble flt-1 as a diagnostic mrker of preeclampsia 2008

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Australian and New Zealand Journal of Obstetrics and Gynaecology 2008; 48: 64–70 DOI: 10.1111/j.1479-828X.2007.00804.x

64 © 2008 The Authors

Journal compilation © 2008 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists

BlackwellPublishing Asia

Original Article

Soluble Flt-1 as a diagnostic marker of pre-eclampsia

Jane WOOLCOCK,1 Annemarie HENNESSY,2 Bei XU,3 Charlene THORNTON,2 Jane TOOHER,1

Angela MAKRIS4 and Robert OGLE1

1Department of Obstetrics and Gynecology, Royal Prince Alfred Hospital, Camperdown, New South Wales, 2School of Medicine, University

of Western Sydney, Penrith, New South Wales, 3Vascular Immunology Research Group, Heart Research Institute, Camperdown, New South

Wales, 4Department of Renal Medicine, Liverpool Hospital, Sydney, New South Wales, Australia

Backgound: Serum levels of soluble fms-like tyrosine kinase (sFlt-1) increase in pre-eclampsia (PE).

Aims: To determine whether concentrations of serum sFlt-1 can differentiate PE or superimposed PE (SPE)

from gestational hypertension (GH) or chronic hypertension (CH).

Methods: Blood was collected from pregnant women being investigated for hypertension (blood pressure of

> 140 and/or 90 mmHg). Normotensive (NP) and pre-eclamptic (PE-C) control ranges were measured.

Results: Patients with evolving hypertension in pregnancy eventually fell into four groups: GH (n = 14), PE

(n = 7), CH (n = 9) and SPE (n = 9). Patients who later developed pre-eclampsia had a higher sFlt-1 (PE:

2.61 ng/mL and SPE: 2.77 ng/mL, respectively) than GH (P < 0.001) or CH (1.05 ng/mL, P = 0.11). Women

with established PE at recruitment (PE-C; (n = 18) (3.13 ng/mL; interquartile range (IQR): 2.14–4.17 ng/mL)

had a median sFlt-1 higher than NP (n = 18) (0.47 ng/mL; IQR: 0.11–0.89) (P < 0.0008). Patients with GH

compared to NP had a slight increase (1.33 ng/mL, P < 0.003). Using a sFlt-1 cut-off of ≥ 1.9 ng/mL yielded

a sensitivity of 94% (95% confidence interval (CI) 73–100%) and specificity of 78% (95% CI 64–82%).

Conclusions: sFlt-1 was elevated in women with PE compared to NP. The sFlt-1 also differentiated women

destined to develop PE among those who presented with a diagnostic rise in maternal blood pressure. The

sFlt-1 test is a useful diagnostic test for PE.

Key words: diagnostic, hypertension, pre-eclampsia, pregnancy, sflt-1.

Background

Pre-eclampsia affects around 5% of pregnancies

causing substantial maternal and fetal morbidity and

mortality,1 although the aetiology and pathogenesis of

pre-eclampsia remain largely unknown. It has been

hypothesised that the initial cause is abnormal

implantation of the placenta resulting in impaired

placental blood flow.1 The hypoxic placenta releases

soluble factors into the maternal circulation, which

induces systemic endothelial dysfunction. This gives

rise to the clinical features of hypertension, proteinuria,

oedema and coagulation abnormalities.1

The circulating factor or factors secreted by the

placenta that are responsible for the widespread

endothelial dysfunction in pre-eclampsia have been

difficult to elucidate despite extensive efforts. Maynard

et al . and others discovered the placenta of pregnant

women with pre-eclampsia produced increased levels

of soluble fms-like tyrosine kinase 1 receptor (sFlt-1).2,3

They also demonstrated that exogenous sFlt-1

administered to pregnant rats produces hypertension,

proteinuria and histological glomeruloendotheliosis,

which are all features of human pre-eclampsia.

Makris et al . have recently proved that elevated sFlt-1

is caused by placental ischaemia.4

sFlt-1 acts by binding to the receptor binding

domains of vascular endothelial growth factor (VEGF)

and placental growth factor (PlGF), another member

Correspondence: Professor Annemarie Hennessy,

University of Western Sydney, Locked Bag 1797,

Penrith South DC, NSW 1797, USA.

Email: [email protected]

This research was undertaken under the auspices of a

grant provided by the ANZCOG.

Received 01 June 2007; accepted 07 November 2007.



sFlt-1 as a diagnostic marker of pre-eclampsia

© 2008 The Authors 65

Journal compilation © 2008 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists; 48: 64–70

of the VEGF family that is made predominantly by

the placanta.2 VEGF is known to have potent

angiogenic properties and also promotes vasodilation.5

VEGF exerts its biological effects through Flt-1, a

membrane-bound receptor tyrosine kinase. sFlt-1 is

the soluble secreted variant of this receptor which

lacks the transmembrane and cytoplasmic domains

and antagonises VEGF and PlGF.6 Increased levels of

sFlt-1 in the maternal circulation will therefore result

in reduced levels of free VEGF and free PlGF, creating

an antiangiogenic state that may be responsible for

the hypertension and proteinuria of pre-eclampsia.2

Levine et al . demonstrated that increased levels

of sFlt-1 and reduced levels of PlGF predict the

development of pre-eclampsia up to five weeks

before the onset of clinical symptoms in stored

blood samples.7

This study aimed to determine if sFlt-1 levels at

the time of first elevation in blood pressure could be

used to differentiate pre-eclampsia from gestational

hypertension (GH) and escalating chronichypertension (CH). Women who have CH develop

pre-eclampsia with increased frequency and severity

and it is often difficult to diagnose pre-eclampsia

due to the similarity of signs.8 An accurate diagnostic

test for pre-eclampsia would be especially useful

for this group of patients. We hypothesised that sFlt-1

would be elevated in patients who were subsequently

proven on clinical grounds to have progressed to

pre-eclampsia.

Methods

Patients were selected prospectively from ward or

delivery suite admissions, day stay assessment or

antenatal clinic at Royal Prince Alfred Women and

Babies, a large teaching hospital in Sydney, Australia.

Subjects were recruited consecutively by a single

clinician. Patients were being investigated for a new

rise in blood pressure (systolic blood pressure of

≥ 140 mmHg or diastolic blood pressure of ≥ 90 mmHg

on at least two occasions > 4 h apart). They were

assessed in four groups according to their final

diagnosis: GH (n = 14), pre-eclampsia (n = 7), CH

(n = 9), and superimposed pre-eclampsia (SPE,

n = 9). Data were established for normotensive

controls (NP, n = 18) and women with pre-eclampsia

at presentation (pre-eclampsia controls: PE-C,

n = 18). Results for CH and gestational hypertension

were also compared to NP.

Pre-eclampsia was defined as hypertension with

at least one other feature of pre-eclampsia. These

included proteinuria (one dipstick measurement

≥ 2+ or ≥ 300 mg in a 24-h urine collection), reduced

platelet count < 150 × 109/L, elevated liver function

tests (alanine aminotransferase > 35 iu/L) or birthweight

below the third centile, according to the classification

system of the Australasian Society for the Study of

Hypertension in Pregnancy (ASSHP).8 Chronic

hypertension was defined as blood pressure requiring

treatment with antihypertensive medication outside

pregnancy or an antenatal blood pressure at less than

20 weeks gestation of ≥ 140/90 mmHg on more than

two occasions at least four hours apart which was

treated and controlled to below 140/90 prior to

inclusion in the study. A final diagnosis was made

post-partum as to whether patients had developed

additional defining features of pre-eclampsia.

Normotensive controls were matched by age

(within two years) and gestation (within one week) to

control patients with pre-eclampsia, that is, patients

with pre-eclampsia at the time of recruitment. Normal

pregnancies were not complicated by medical or

obstetric complications and delivered an infant of greater than 2500 g at term. Pre-eclampsia controls

had diagnostic features of pre-eclampsia, as described

above at the time of presentation.

All women provided written informed consent

prior to collection of serum samples, which were

collected between March 2005 and January 2006.

This study was approved by the Ethics Committee of

Royal Prince Alfred Hospital in accordance with

National Health and Medical Research Council

Guidelines for Human Research.

Venepuncture, using an 18-gauge needle and

vacutainer system at the cubital fossa, was performedat the time of recruitment and blood collected into

tubes containing EDTA. The samples were centrifuged

within four hours of collection and the serum stored

at –70°C. The concentrations of sFlt-1 were measured

with the use of enzyme-linked immunosorbent assay

(ELISA) from BD (San Jose, CA, USA) by a single

operator. The person who performed the assay was

blinded to the clinical diagnoses of the patients. All

measurements were made in duplicate on 1:2 dilution

of the sera. The microtitre plates were read with a

programmable spectrophotometer.

Data were analysed using Minitab 10, utilising

Kruskal–Wallis and Mann–Whitney tests for non-

parametric data. Data are presented as medians and

interquartile ranges. Significance was assumed for a

P -value of < 0.05. Sensitivity, specificity, positive

predictive value, negative predictive value, positive

likelihood ratio and negative likelihood ratio were

calculated using an arbitrary cut-off of serum sFlt-1

at 1.9 ng/mL.



J. Woolcock et al .



Results

There were no significant differences in mean

gestation and maternal age between the four groups

(Table 1). Serum samples were taken at a median of

35 weeks and three days gestation (range 25–41

weeks) and a median of 2.6 weeks before delivery(range 0–11 weeks).

At recruitment in the CH and PE groups, 83%

and 94% of patients, respectively, were being

treated with antihypertensive medications, while

only 24% of patients with new onset hypertension

in the GH group were being treated. These medications

included clonidine (81% n = 29), hydralazine (31%

n = 11), oxprenolol (14% n = 5), labetalol (8% n = 3)

and methyldopa (6% n = 2). At delivery all patients

were being treated with antihypertensive medications

and 19% (n = 13) of patients were on more than

one type of antihypertensive medication. All

patients in the PE-C group and no patients in the

NP group were on blood pressure lowering

medications (Table 2).

Of the 21 patients with an uncertain diagnosis at

recruitment, 33% (n = 7) developed features of

pre-eclampsia, while 50% (n = 9) of patients with CH

progressed to SPE. Of the seven pre-eclamptic

patients, one patient was being treated with

intravenous antihypertensive medication and one

patient was treated with magnesium sulphate as an

anticonvulsant. Of the nine patients with SPE, two

patients required intravenous therapy and one

patient was being treated with magnesium sulphate.

In the PE-C group, 59% (n = 10) of patients were

being treated with more than one antihypertensiveagent at delivery and 23% (n = 4) were on

magnesium sulphate.

Figure 1 shows the concentrations of sFlt-1

according to diagnosis as confirmed post-partum.

Women with pre-eclampsia at recruitment (PE-C)

had a median serum concentration of sFlt-1 higher

than women with NP (PE-C: median 3.13 ng/mL

interquartile range (IQR) 2.14–4.17 ng/mL and NP:

0.47 ng/mL IQR 0.11–0.89 ng/mL; P < 0.0008).

Patients with elevated blood pressure at recruitment

(Fig. 2) who later developed features of pre-eclampsia

had a higher median serum concentration of sFlt-1

than GH or CH (PE: median 2.61 ng/mL, IQR

1.9–2.69 ng/mL < 0.00 and SPE: 2.77 ng/mL, IQR

2.45–3.65 ng/mL P < 0.001). Patients with GH

compared to normal pregnancy had a slight increase

(1.33 ng/mL, IQR 1.06–1.77 ng/mL P < 0.003),

whereas those with a final diagnosis of CH were

not different to normal (1.05 ng/mL IQR 0.38–

1.83 ng/mL, P = 0.11).

Table 1 Clinical characteristics of women with recently elevated blood pressure

Final diagnosis GH PE CH SPE *P -value

Maternal age,

years (IQR)

29.5 (26–35) 31 (28–33) 32 (28–35) 34 (30–36) NS

Gestation at trial entry,

weeks (IQR)

36 (29–39) 34 (32–35) 36 (29–39) 34 (29–38)

Delivery gestation,weeks (IQR)

37 (36–39) 35 (33–38) 37 (36–40) 36 (30–39) NS

Birthweight,

g (IQranger)

3188 (2973–3768) 2530 (2108–2579) 2828 (1568–3328) 2500 (1111–3196) P < 0.008

CH, chronic hypertension; GH, gestational hypertension; IQR, interquartile range; NS, not significant; PE, certain

pre-eclampsia; SPE, superimposed pre-eclampsia.

Table 2 Clinical characteristics of controls

Final diagnosis NP PE-C *P -value

Maternal age, years (IQR) 32 (28–39) 32 (28–38) NS

Delivery gestation, weeks (IQR) 40 (39–40) 36 (33–38) NS

Birthweight, g (IQR) 3463 (3131–3866) 2562 (2006–3279) P < 0.008

IQ, interquartile; NP, normal pregnancy; NS, not significant; PE-C, pre-eclampsia controls.






Using a sFlt-1 cut-off of ≥ 1.9 ng/mL this test yielded

a sensitivity of 94% (95% confidence interval (CI)

73–100%) and specificity of 78% (95% CI 64–82%).

Of the 16 women who developed pre-eclampsia after

recruitment, nine (56%) had an elevated sFlt-1 level,

≥ 1.9 ng/mL, up to eight weeks before the onset of

pre-eclampsia. The positive likelihood ratio for this test

is 4.3 (95% CI 1.762–8.553) and the negative likelihood

ratio is 0.08 (95% CI 0.018–0.540) (Table 3).

There were five patients included in the data

analysis with particularly high levels of sFlt-1 at

recruitment. These values were 7.34, 5.45, 5.16, 4.82and 4.78 ng/mL. These patients all had evidence of

severe disease. All five patients were being treated

with intravenous antihypertensive therapy for blood

pressure ≥ 170/110 and four women were being treated

with magnesium sulphate at delivery. All five babies

were delivered prematurely at 28, 31, 33, 34 and 35

weeks gestation because of worsening pre-eclampsia.

Discussion

Our findings confirm that the maternal serum sFlt-1

concentration is markedly increased in women withpre-eclampsia when compared with controls. We

have also shown that in women with a new onset

rise in blood pressure, serum sFlt-1 concentrations

can ‘diagnose’ pre-eclampsia a maximum of eight

weeks before the onset of additional clinically

defining features. This study has also found that very

high levels of sFlt-1 were present in patients with

severe pre-eclampsia.

This study extends prior observations by

examining serum sFlt-1 concentrations in patients

with CH. Our data show that sFlt-1 levels may be a

useful test for this group of women at high risk of

developing SPE.

No single test exists to identify which women with

new onset ‘gestational’ hypertension or escalating

CH will develop pre-eclampsia. Serum uric acid

concentration has been suggested as one of the most

sensitive indicators of pre-eclampsia.9 Decreased

renal tubular excretion is the most likely mechanism

for uric acid being increased in pre-eclampsia.10,11

Figure 1 Serum sFlt-1 concentrations in normal

pregnancy and in patients with pre-eclampsia at

presentation. Individual patient data; median and

interquartile ranges shown. **P < 0.001 compared to

normal pregnancy.

Figure 2 Serum sFlt-1 concentrations at the time of

recent elevation in blood pressure according to final

diagnosis. Individual patient data; median and interquartile

ranges shown. **P < 0.001 compared to gestational

hypertension and chronic hypertension.

Table 3 Serum sFlt-1 as a diagnostic marker for

pre-eclampsia for sFlt-1 concentration ≥ 1.9 ng/mL

95% CI

Sensitivity 94% 73–100%

Specificity 78% 64–82%

Positive predictive value 75% 59–80%

Negative predictive value 95% 77–100%Positive likelihood ratio 4.3 1.97–9.46

Negative likelihood ratio 0.08 0.018–0.540

CI, confidence interval.



J. Woolcock et al .



Oxidative stress may also give rise to the hyper-

uricaemia seen in pre-eclampsia.12 Serum uric acid

levels used for the diagnosis of pre-eclampsia gave a

sensitivity of 69% and specificity of 51% with a cut-off

of 0.33 mmol/L.13 There may be some correlation

between elevated serum uric acid levels and both the

severity of pre-eclampsia and the neonatal morbidity.14–16

The clinical utility of serum uric acid values in

differentiating various hypertensive diseases of

pregnancy, however, appears to be limited.17

Serum creatinine levels have also been used to help

confirm a diagnosis of pre-eclampsia. A level greater

then 106 µmol/L in pregnancy supports the diagnosis

of pre-eclampsia;18 however, levels may not help

differentiate CH because of underlying renal disease.9

Some investigators have retrospectively looked at

the usefulness of Down syndrome screening markers

for the prediction of pre-eclampsia. Second trimester

serum levels of alpha-fetoprotein (AFP), human

chorionic gonadotrophin (hCG), unconjugated estriol

(uE3) and inhibin A (inh A) have been usedindividually and in combination for risk assessment of

pre-eclampsia. The most promising of these markers

seems to be inh A, which has been reported to be

significantly increased in the second trimester in

women destined to develop pre-eclampsia with a

sensitivity of up to 48% for a specificity of 90%.19 inhA

may be useful for the prediction of pre-eclampsia

as early as ten weeks gestation;20 however, levels

appear to be more markedly increased closer to

disease onset in pre-eclamptic women.21 In a small

study, Wald et al . reported that combining the values

of inh A, hCG and uE3 from second trimestermaternal screening would detect women who would

subsequently develop pre-eclampsia in their pregnancy

with a sensitivity of 55% and specificity of 95%.22

Second trimester serum markers combined with

other maternal indices show greater predictive value.

For example maternal age, body mass index and

parity with free βhCG predicted 70% of women who

developed pre-eclampsia with a specificity of 71%.23

inh A with Doppler ultrasound predicted 71% of

cases of pre-eclampsia with a specificity of 93%.24

Longitudinal blood sampling has shown that

leptin concentrations are increased in established

pre-eclampsia, as well as before pre-eclampsia is

clinically evident from 20 weeks gestation until delivery.25

Serum leptin and placental growth factor in combination

have been used as a screening test for pre-eclampsia

at 24 weeks gestation with reported sensitivity of 67%

for a specificity of 100%. These authors also showed

a decrease in insulin-like growth factor binding

factor-1 prior to the onset of pre-eclampsia.26

Fibronectin levels, a marker of endothelial

dysfunction, are elevated up to four weeks before the

onset of pre-eclampsia.27,28 A longitudinal study of

378 women showed as early as nine to 12 weeks of

gestation, there was a difference in fibronectin levels

between women who developed pre-eclampsia in their

pregnancy and controls. At 22–26 weeks gestation the

sensitivity of fibronectin for predicting pre-eclampsia

was 73% with a specificity of 87%.29

Similarities between pre-eclampsia and insulin

resistance syndrome have led to theories that

measurements of glucose tolerance and insulin resistance

may predict pre-eclampsia. A recent study has shown

that fasting insulin sensitivity indexes can predict in

early (16–20 weeks) and late (26–30 weeks) pregnancy

the subsequent development of pre-eclampsia with a

sensitivity of 85% and 88%, respectively, for a

specificity of 97%.30

Placental sFlt-1 has been implicated as being

involved in the pathophysiology of pre-eclampsia

by disrupting maternal endothelial cell functionthrough antagonism of VEGF. sFlt-1 concentrations

in pre-eclamptic women were more than threefold

over the control which helps to confirm this hypothesis.

The findings of this study are consistent with

previous studies which have also found elevated

concentrations of sFlt-1 in patients with pre-eclampsia

at the time of diagnosis.2,31,32 A longitudinal study of

eight women who developed pre-eclampsia, six with

hypertension only (four CH and two gestational

hypertension) and nine with normal pregnancy showed

that sFlt-1 was significantly higher at 25–28 weeks in

women who developed pre-eclampsia compared towomen with hypertension alone or normal pregnancy.

The group with hypertension alone appeared not to

have substantially higher levels than women with

normal pregnancy.33

A larger longitudinal analysis of serum sFlt-1

concentrations in normal pregnancy and pre-

eclampsia showed that sFlt-1 levels were increased

only within five weeks before the onset of hypertension

and proteinuria.7

Pre-eclampsia causes significant morbidity and

methods for early identification and streamlined

management of women destined to develop pre-

eclampsia are needed urgently. In this cohort of women

there was a clear elevation in sFlt-1 at presentation

with pre-eclampsia compared to normotensive controls.

The sFlt-1 concentration also differentiated women

destined to develop pre-eclampsia from those with

CH and those who had presented with a diagnostic

rise in maternal blood pressure with no other feature

of pre-eclampsia (gestational hypertension).






This test has important clinical utility as it targets

patients at high risk of developing pre-eclampsia, that

is, those women with uncertainty in their diagnosis.

Serum sFlt-1 measurements could be used to guide

important management decisions regarding whether

or not admission to hospital is required, closer

monitoring in a day-stay unit or consideration of

delivery. To reduce the risks that are associated with

the development of severe pre-eclampsia, early detection

and timely assessment of the disease are essential.

Serum sFlt-1 appears to be a useful tool as a one-off

test in the third trimester for patients with clinical

uncertainty of the cause of hypertension in pregnancy.

References

1 Roberts J, Lain K. Recent insights into the

pathogenesis of preeclampsia. Placenta 2002; 23:

359–372.

2 Maynard S, Min J, Merchan J et al . Excess

placental soluble fms-like tyrosine kinase 1 (sFlt1)may contribute to endothelial dysfunction, hypertension

and proteinuria in preeclampsia. J Clin Invest 2003;

111: 649–658.

3 Zhou Y, McMaster M, Woo K et al . Vascular

endothelial growth factor ligands and receptors that

regulate human cytotrophoblast survival are

dysregulated in severe preeclampsia and hemolysis,

elevated liver enzymes and low platelets syndrome. Am J Pathol 2002; 160: 1405–1423.

4 Makris A, Thornton C, Thompson J et al .

Uteroplacental ischemia results in proteinuric

hypertension and elevated sFLT-1. Kidney Int 2007:

Epub Mar 21.5 He H, Venema VJ, Gu X, Venema RC, Marrero MB,

Caldwell RB. Vascular endothelial growth factor

signals endothelial cell production of nitric oxide and

prostacyclin through Flk-1/KDR activation of c-Src. J Biol Chem 1999; 274: 25130–25135.

6 Shibuya M. Structure and function of VEGF/VEGF-

receptor system involved in angiogenesis. Cell Struct

Funct 2001; 26: 25–35.

7 Levine R., Maynard S, Qian C et al . Circulating

angiogenic factors and the risk of preeclampsia. N

Engl J Med 2004; 350: 672–683.

8 Brown MA, Hague WM, Higgins J et al . Australasian

Society for the Study of Hypertension in Pregnancy.

The detection, investigation and management of hypertension in pregnancy: Executive summary.

Aust N Z J Obstet Gynaecol 2000; 40: 133–138.

9 Roberts J. Pregnancy-related hypertension. In: Creasy

R, Resnick R, eds. Maternal-Fetal Medicine, 4th edn.

Philadelphia, PA: W.B. Saunders Company, 1999;

833–871.

10 Chesley L, Williams L. Renal glomerular and

tubular function in relation to the hyperuricaemia of

preeclampsia and eclampsia. Am J Obstet Gynecol

1945; 50: 367–375.

11 Boyle J, Campbell S, Duncan A. Serum uric acid

levels in normal pregnancy with observations on the

renal excretion of urate in pregnancy. J Clin Pathol

1966; 19: 501–503.

12 Many A, Hubel C, Roberts J. Hyperuricaemia and

xanthine oxidase in preeclampsia, revisited. Am J

Obstet Gynecol 1996; 174: 288–291.13 Shuster E, Weppelman B. Plasma urate measurements

and fetal outcome in preeclampsia. Gynecol Obstet

Invest 1981; 12: 162.

14 Acien P, Lloret G, Lloret M. Perinatal morbidity

and mortality in pregnancy hypertensive disorders:

Prognostic value of the clinical and laboratory

findings. Int J Gynaecol Obstet 1990; 32: 229–235.

15 Redman C, Beilin L, Bonnar J, Wilkinson R.

Plasma-urate measurements in predicting fetal death

in hypertensive pregnancy. Lancet 1976; 1: 1370–1373.

16 Sagen N, Kjell H, Nilsen S. Serum urate as a

predictor of fetal outcome in severe preeclampsia. Acta Obstet Gynecol Scand 1984; 63: 71–75.

17 Lim K, Friedman S, Ecker J, Kao L, Kilpatrick S.The clinical utility of serum uric acid measurements

in hypertensive diseases of pregnancy. Am J Obstet

Gynecol 1998; 178: 1067–1071.

18 Report of the National High Blood Pressure Education

Program Working Group on High Blood Pressure in

Pregnancy. Am J Obstet Gynecol 2000; 183: S1–S22.

19 Aquilina J, Barnett A, Thompson O, Harrington K.

Second-trimester maternal serum inhibin A

concentration as an early marker for preeclampsia. Am J Obstet Gynecol 1999; 181: 131–136.

20 Sebire N, Roberts L, Noble P, Wallace E, Nicolaides

KH. Raised maternal serum inhibin A concentration

at 10–14 weeks of gestation is associated withpreeclampsia. Br J Obstet Gynaecol 2000; 107: 795–797.

21 Lambert-Messerlain G, Silver H, Petraglia F et al .

Second trimester levels of maternal serum human

chorionic gonadotrophin and inhibin A as predictors

of preeclampsia in the third trimester of pregnancy. J

Soc Gynecol Invest 2000; 7: 170–174.

22 Wald N, Morris J. Multiple marker second trimester

serum screening for preeclampsia. J Med Screen 2001;

8: 65–68.

23 Lee L, Sheu B, Shau W et al . Mid-trimester β-hCG

levels incorporated in a multifactorial model for

prediction of severe preeclampsia. Prenat Diagn 2000;

20: 738–743.

24 Aquilina J, Thompson O, Thilaganathan B,Harrington K. Improved early prediction of

preeclampsia by combining second-trimester maternal

serum inhibin-A and uterine artery Doppler.Ultrasound Obstet Gynecol 2001; 17: 477–484.

25 Anim-Nyame N, Sooranna S, Steer P, Johnson MR.

Longitudinal analysis of maternal plasma leptin

concentrations during normal pregnancy and

preeclampsia. Hum Reprod 2000; 15: 2033–2036.



J. Woolcock et al .



26 Anim-Nyame N, Hills FA, Sooranna SR, Steer PJ,

Johnson MR. A longitudinal study of maternal plasma

insulin-like growth factor binding protein-1

concentrations during normal pregnancy and

pregnancies complicated by pre-eclampsia. Hum

Reprod 2000; 15: 2215–2219.

27 Ballegeer V, Spitz B, Kieckens L, Moreau H, Van

Assche A, Collen D. Predictive value of increased

plasma levels of fibronectin in gestational hypertension. Am J Obstet Gynecol 1989; 161: 432–436.

28 Lazarchik J, Stubbs T, Romein L, Van Dorsten JP,

Loadholt CB. Predictive value of fibronectin levels

in normotensive gravid women destined to become

preeclamptic. Am J Obstet Gynecol 1986; 154:

1050–1052.

29 Chavarria M, Lara-Gonzalez L, Gonzalez-Gleason A,

Sojo I, Reyes A. Maternal plasma cellular fibronectin

concentrations in normal and preeclamptic pregnancies:

A longitudinal study for early prediction of

preeclampsia. Am J Obstet Gynecol 2002; 187: 595–601.

30 Parretti E, Lapolla A, Dalfra M et al . Preeclampsia in

lean normotensive normotolerant pregnant women

can be predicted by simple insulin sensitivity indexes.Hypertension 2006; 47: 449–453.

31 Koga K, Osuga Y, Yoshino O et al . Elevated serum

soluble vascular endothelial growth factor receptor 1

(sVEGFR-1) levels in women with preeclampsia. J Clin Endocrinol Metab 2003; 88: 2348–2351.

32 Chaiworapongsa T, Romero R, Espinoza J et al .Evidence supporting a role for blockade of the

vascular endothelial growth factor system in the

pathophysiology of preeclampsia. Am J Obstet Gynecol

2004; 190: 1541–1547.

33 Hertig A, Berkane N, Lefevre G et al . Maternal

serum sFlt1 concentration is an early and reliable

predictive marker of preeclampsia. Clin Chem 2004;

50: 1702–1703.

34 Levine R, Maynard S, Qian C et al . Circulating

angiogenic factors and the risk of preeclampsia. N

Engl J Med 2004; 350: 672–683.

soluble flt-1 as a diagnostic mrker of preeclampsia 2008

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