What laboratory tests are recommended for the diagnosis and management of preeclampsia?

Preeclampsia Laboratory Tests

The essential laboratory tests for preeclampsia diagnosis and management include blood pressure monitoring, proteinuria assessment, and a minimum of twice weekly blood tests for hemoglobin, platelet count, liver enzymes, and renal function including uric acid. 1

Core Diagnostic Tests

• Proteinuria assessment: Initially screen with automated dipstick urinalysis, then if positive, quantify with urine protein/creatinine ratio (abnormal if ≥30 mg/mmol or 0.3 mg/mg) 1, 2
• Blood pressure monitoring: Essential for diagnosis and ongoing management, with severe hypertension defined as >160/110 mmHg 1
• Complete blood count: Particularly hemoglobin and platelet count, with thrombocytopenia (<100,000/mm³) being a severity marker 1
• Liver function tests: Including transaminases to detect liver involvement 1
• Renal function tests: Creatinine and uric acid (elevated uric acid associated with worse maternal and fetal outcomes) 1, 2

Frequency of Monitoring

• At diagnosis: Complete initial laboratory panel to establish baseline values 1
• Ongoing monitoring: Minimum twice weekly blood tests for hemoglobin, platelet count, liver enzymes, and renal function in women with preeclampsia 1
• More frequent testing: Required with clinical deterioration or changes in maternal condition 1

Severity Indicators

• Progressive thrombocytopenia: Indicates worsening disease and is an indication for delivery 1, 3
• Progressively abnormal liver enzymes: Particularly concerning when accompanied by right upper quadrant or epigastric pain 1
• Worsening renal function: Progressive elevation in creatinine 1, 2
• Hemolysis: May indicate development of HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets) 4

Special Considerations

• Magnesium sulfate monitoring: When administering for seizure prophylaxis, monitor deep tendon reflexes, respiratory rate, and serum magnesium levels (therapeutic range: 3-6 mg/100 mL) 5
• Coagulation studies: Consider in severe preeclampsia with platelet counts <100,000/mm³ 3, 6
• Urine output monitoring: Should be maintained at ≥100 mL over four hours preceding each magnesium sulfate dose 5

Clinical Pitfalls to Avoid

• Relying solely on proteinuria: The American College of Obstetricians and Gynecologists no longer requires proteinuria for diagnosis of preeclampsia 4
• Using uric acid or proteinuria levels alone as indications for delivery: These should not be used in isolation to determine timing of delivery 1
• Attempting to clinically distinguish mild versus severe preeclampsia: All cases may rapidly progress to emergencies 1
• Inadequate monitoring frequency: Failure to perform twice weekly laboratory testing may miss disease progression 1
• Overlooking baseline laboratory tests: Essential for detecting subsequent abnormalities, especially in women with chronic hypertension 7

Indications for Delivery Based on Laboratory Results

• Progressive thrombocytopenia: Indicates need for delivery regardless of gestational age 1
• Progressively abnormal renal or liver enzyme tests: Key indicators for delivery 1
• Severe hypertension unresponsive to treatment: Particularly with BP >160/110 mmHg despite three antihypertensive agents 1

Laboratory monitoring is crucial for both diagnosis and ongoing management of preeclampsia, with abnormal results often guiding critical decisions about timing of delivery to prevent serious maternal and fetal complications 1, 4.