What is the latest approach to preeclampsia screening?

Current Approach to Preeclampsia Screening

Blood pressure measurement remains the primary screening method for preeclampsia, while newer biomarker tests like the sFlt-1/PlGF ratio show promise for predicting preterm preeclampsia but are not yet recommended for routine clinical use. 1

Standard Screening Approach

Blood Pressure Measurement

• The USPSTF strongly recommends screening all pregnant women for preeclampsia with blood pressure measurements throughout pregnancy (Grade B recommendation) 1
• Proper technique is essential:
  • Patient should be relaxed, quiet, and sitting with legs uncrossed and back supported
  • Arm positioned at the level of the right atrium of the heart
  • Use large blood pressure cuff if upper arm circumference ≥33 cm
  • Avoid measuring BP in left lateral position (falsely lowers readings)
  • Confirm elevated readings with repeated measurements 1

Screening Interval

• BP measurements should be obtained at every prenatal visit throughout pregnancy
• More frequent monitoring for women with risk factors 1

Risk Assessment

High-Risk Factors

• History of preeclampsia (particularly early-onset)
• Previous adverse pregnancy outcome
• Maternal comorbidities:
  • Type 1 or 2 diabetes
  • Gestational diabetes
  • Chronic hypertension
  • Renal disease
  • Autoimmune diseases
• Multifetal gestation
• Nulliparity
• Obesity
• African American race
• Low socioeconomic status
• Advanced maternal age 1

Emerging Biomarker Tests

sFlt-1/PlGF Ratio

• Shows promise for predicting preterm preeclampsia
• A low sFlt-1/PlGF ratio can rule out preeclampsia development within 4 weeks
• A high ratio predicts preeclampsia occurrence within 1 week 2
• The UK's NICE group has recommended the Elecsys immunoassay for sFlt-1/PlGF ratio or Triage PlGF test to help rule out preeclampsia in women with suspected disease between 20-34+6 weeks' gestation 1
• However, ISSHP guidelines state these tests should not be used routinely as rule-out tests until further clinical studies are conducted 1

First Trimester Multivariable Screening

• The Fetal Medicine Foundation (FMF) "triple test" combines:
  • Maternal risk factors
  • Mean arterial pressure
  • Uterine artery pulsatility index
  • Serum placental growth factor (PlGF)
• Detection rates of 90% for early and 75% for preterm preeclampsia (10% false-positive rate)
• Superior to traditional risk factor screening alone 3
• In the ASPRE study, this screening approach followed by aspirin prophylaxis reduced preterm preeclampsia by 62% 1, 3

Prevention Strategies

Low-Dose Aspirin

• Recommended for women at high risk of preeclampsia
• Dose: 81-162 mg/day (optimal dose may be 150 mg at night)
• Start before 16 weeks gestation (ideally by 12 weeks)
• Continue until 36-37 weeks gestation 1, 4
• The ASPRE trial confirmed that 150 mg aspirin at night is safe for pregnant women 1

Calcium Supplementation

• Recommended for women with low calcium intake
• Dose: 1.2-2.0 g/day in divided doses (≤500 mg per administration)
• Start at first antenatal contact or by 20 weeks gestation
• Continue until delivery
• Reduces preeclampsia risk by approximately 50% in women with low dietary calcium intake 4

Pitfalls and Limitations

1. Biomarker Testing Limitations:

   • Most specialized tests are not yet validated for routine clinical use
   • Cost-effectiveness of widespread implementation remains uncertain
   • Requires standardized protocols and quality control 1

2. Risk Factor Assessment Limitations:

   • NICE and ACOG risk factor approaches have suboptimal performance
   • NICE recommendations achieve only 41% detection rate for preterm preeclampsia
   • 2013 ACOG recommendations achieve only 5% detection rate for preterm preeclampsia 3

3. Implementation Challenges:

   • Specialized tests like uterine artery Doppler require trained personnel
   • Biomarker testing may not be available in all settings, particularly in low-resource areas 1

Current Best Practice

1. Universal BP screening at all prenatal visits for all pregnant women 1

2. Risk assessment using maternal history and clinical factors 1

3. Low-dose aspirin (150 mg at night) for high-risk women, starting before 16 weeks 1, 4

4. Calcium supplementation (1.2-2.0 g/day) for women with low calcium intake 4

5. Consider specialized testing (sFlt-1/PlGF ratio or FMF triple test) in select clinical scenarios and where available, but not for routine screening 1

While promising biomarker tests are emerging, blood pressure measurement remains the cornerstone of preeclampsia screening, with specialized biomarker tests serving as adjuncts in specific clinical scenarios rather than as primary screening tools.