What laboratory tests are indicated for the evaluation of preeclampsia?

Laboratory Tests for Evaluation of Preeclampsia

The evaluation of preeclampsia requires a comprehensive panel of laboratory tests including complete blood count with platelets, liver function tests, renal function tests, and urinalysis to assess maternal organ dysfunction. 1, 2

Essential Laboratory Tests

First-line Tests (Required for All Suspected Cases)

• Complete Blood Count (CBC) with platelet count 1, 2
• Liver function tests:
  • Aspartate aminotransferase (AST)
  • Alanine aminotransferase (ALT)
  • Lactate dehydrogenase (LDH)
  • Serum bilirubin
  • Serum albumin 1, 2
• Renal function tests:
  • Serum creatinine
  • Blood urea nitrogen (BUN)
  • Serum uric acid 1, 2, 3
• Urinalysis and protein quantification:
  • Protein-to-creatinine ratio (PCR) or
  • Albumin-to-creatinine ratio (ACR) or
  • 24-hour urine protein collection 1

Coagulation Studies

• Activated partial thromboplastin time (aPTT) - abnormal in up to 42% of eclampsia cases 4
• Fibrinogen levels - to assess for potential disseminated intravascular coagulation (DIC) 1, 4

Rationale for Testing

Hematological Assessment

Platelet count is critical as thrombocytopenia (<100×10^9/L) is associated with increased risk of abnormal coagulation and adverse maternal outcomes 1. Decreasing platelet counts may indicate worsening disease severity and potential development of HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets).

Liver Function Evaluation

Elevated liver enzymes reflect hepatic involvement in preeclampsia and are significantly higher in preeclamptic women compared to normotensive pregnant women 3. These abnormalities are frequently associated with adverse maternal outcomes in HELLP syndrome, though they should not be used in isolation to guide care 1.

Renal Function Assessment

Serum creatinine and uric acid are important markers of renal dysfunction in preeclampsia. Hyperuricemia is considered a predictor of preeclampsia severity and indicates kidney dysfunction 3. Abnormal renal function tests are common in preeclampsia and warrant careful monitoring 5.

Proteinuria Assessment

While proteinuria is present in approximately 75% of preeclampsia cases, it is not required for diagnosis according to current guidelines 1. However, quantification of proteinuria remains important for assessment of disease severity and progression.

Frequency of Testing

For women diagnosed with preeclampsia, laboratory monitoring should increase to twice weekly in later pregnancy or with any concerning symptoms 2. More frequent testing may be necessary with disease progression or development of severe features.

Special Considerations

• Women with chronic hypertension should have baseline laboratory tests performed at first diagnosis to provide reference values if superimposed preeclampsia develops later 1
• In resource-limited settings where same-day laboratory testing is not available, referral to centers with appropriate facilities is necessary for proper evaluation 1
• Abnormal laboratory values should prompt increased surveillance and consideration of delivery timing based on gestational age and disease severity 2

Clinical Application

Laboratory abnormalities that suggest end-organ damage and severe preeclampsia include:

• Platelet count <100×10^9/L
• AST or ALT >2 times upper limit of normal
• Serum creatinine >1.1 mg/dL or doubling of baseline
• LDH elevation (indicating hemolysis)

These findings, particularly when progressive, should prompt consideration of delivery as the definitive treatment for preeclampsia 1, 2.