Diagnostic Criteria for HELLP Syndrome
HELLP syndrome is diagnosed when a pregnant patient presents with evidence of hemolytic anemia, thrombocytopenia (platelets <100,000/mm³), and elevated liver enzymes, typically occurring in the context of preeclampsia after 20 weeks' gestation. 1
Core Diagnostic Components
The diagnosis requires all three of the following laboratory findings 1, 2:
1. Hemolysis - Evidence includes:
- Abnormal peripheral blood smear showing schistocytes or microangiopathic changes 1
- Elevated lactate dehydrogenase (LDH) >600 U/L 2
- Elevated indirect bilirubin 3
- Low serum haptoglobin levels 3
- Increased fibrin degradation products (>10 µg/L) 1
2. Elevated Liver Enzymes:
- Aspartate aminotransferase (AST) ≥70 U/L 2
- Alanine aminotransferase (ALT) elevated (>45 U/L) 1
- LDH >600 U/L 2
3. Low Platelet Count:
Classification Systems
Tennessee Classification System
The most widely referenced criteria require 2:
- Hemolysis with LDH >600 U/L
- AST ≥70 U/L
- Platelets <100 × 10⁹/L
Mississippi Triple-Class System
Further stratifies HELLP by severity based on platelet nadir 2:
- Class 1: Platelets ≤50,000/mm³ (most severe)
- Class 2: Platelets 50,000-100,000/mm³
- Class 3: Platelets 100,000-150,000/mm³
Clinical Context and Presentation
Timing and Associated Features
- Approximately 70% of cases develop antepartum, predominantly between 27-37 weeks' gestation 2
- The remaining 30% occur within 48 hours postpartum 2
- Hypertension (BP >160/90 mmHg) is often present but not required for diagnosis 1, 4
- Proteinuria is present in approximately 75% of cases but not required 1
- One-third of patients may be normotensive at presentation 4
Key Clinical Symptoms to Identify
- Epigastric or right upper quadrant pain (most common presenting symptom) 1, 5, 4
- Upper abdominal tenderness 1
- Nausea and vomiting 1
- Malaise 1
- 14% may be completely asymptomatic at diagnosis 4
Complete vs. Partial HELLP Syndrome
Complete HELLP syndrome requires all three diagnostic components 6. Partial HELLP syndrome (also termed ELLP when hemolysis is absent) presents with only one or two features 6, 7. This distinction is clinically important because complete HELLP syndrome carries significantly higher maternal morbidity, including increased rates of disseminated intravascular coagulation, need for transfusion, and cesarean delivery compared to partial HELLP or severe preeclampsia alone 6.
Essential Laboratory Workup
When HELLP syndrome is suspected, obtain 1:
- Complete blood count with platelet count and peripheral blood smear
- Liver function tests: AST, ALT, LDH, bilirubin (total and indirect), alkaline phosphatase
- Coagulation studies: PT, aPTT, fibrinogen, fibrin degradation products
- Renal function: Creatinine, urea, uric acid
- Hemolysis markers: Haptoglobin, reticulocyte count
Critical Diagnostic Pitfalls
Differential Diagnoses to Exclude
HELLP syndrome can be confused with other conditions that require different management 8:
- Acute fatty liver of pregnancy
- Hemolytic uremic syndrome
- Thrombotic thrombocytopenic purpura
- Acute cholecystitis 1
- Drug reactions 1
- Idiopathic thrombocytopenia 1
Relationship to Preeclampsia
HELLP syndrome is not a separate disorder but represents the severe end of the preeclampsia spectrum 1. It occurs in 10-20% of cases with severe preeclampsia 2. The International Society for the Study of Hypertension in Pregnancy (ISSHP) recommends considering HELLP as part of preeclampsia with maternal organ dysfunction, ensuring all features of preeclampsia are sought and addressed 1.
Prognostic Correlation
The degree of thrombocytopenia correlates directly with the severity of liver dysfunction 1. Lower platelet counts (Mississippi Class 1) indicate more severe disease and higher risk of complications 2. Maternal mortality ranges from 1-24% depending on the series, with significant risks of hepatic rupture, acute renal failure, disseminated intravascular coagulation, and cerebrovascular accidents 1, 2, 4.