Tennessee Criteria for HELLP Syndrome
The Tennessee Classification System diagnoses HELLP syndrome by three mandatory components: hemolysis with LDH >600 U/L, elevated liver enzymes with AST ≥70 U/L, and thrombocytopenia with platelets <100,000/mm³. 1
Diagnostic Criteria
The Tennessee system requires all three of the following laboratory findings to establish the diagnosis:
- Hemolysis: LDH >600 U/L, which serves as a dual marker reflecting both the extent of hemolysis and hepatic dysfunction 2, 1
- Elevated liver enzymes: AST ≥70 U/L (ALT is also typically elevated) 1
- Low platelet count: Platelets <100,000/mm³, which ACOG identifies as the threshold indicating severe thrombocytopenia with significant maternal risk 3, 2
Additional confirmatory findings include:
- Microangiopathic hemolytic anemia confirmed by peripheral blood smear showing schistocytes from endothelial damage with fibrin deposition 2
- Elevated total bilirubin as part of the hemolysis picture 2
Key Distinction from Mississippi Classification
While the Tennessee system provides a binary diagnosis (HELLP present or absent), the Mississippi Triple-class system further stratifies HELLP severity by nadir platelet counts into three classes, with Class 1 defined as platelets ≤50,000/mm³ carrying the highest risk of hemorrhagic complications 1, 4
Clinical Context and Timing
- HELLP typically develops in the third trimester (70% of cases occur before delivery, predominantly between 27-37 weeks gestation) in patients with severe preeclampsia 1, 5
- Approximately 30% of cases occur or worsen postpartum within 48-72 hours after delivery, with laboratory abnormalities peaking at 24 hours postpartum 2, 6
- The syndrome may present as complete (meeting all three criteria) or incomplete (meeting only some criteria) 1, 5
Critical Clinical Correlations
The degree of thrombocytopenia directly correlates with severity of liver dysfunction and predicts adverse maternal outcomes. 3, 2
- Platelet counts ≤40,000/mm³ represent the threshold most predictive of postpartum hemorrhagic complications 4
- Right upper quadrant or epigastric pain (present in 65% of symptomatic patients) should immediately trigger abdominal imaging to rule out subcapsular hematoma or hepatic rupture 3, 2
Essential Laboratory Monitoring
Beyond the diagnostic triad, obtain the following for complete assessment and surgical planning:
- Coagulation studies: PT, PTT, fibrinogen, fibrin degradation products 2
- Renal function: serum creatinine, urea, uric acid 2
- Complete blood count with peripheral smear 2
- Chest X-ray to exclude pulmonary edema 2
Common Pitfall
Do not delay delivery waiting for laboratory values to normalize—HELLP syndrome only resolves after delivery, and maternal mortality reaches 3.4% with delayed intervention. 3 The Tennessee criteria establish diagnosis to trigger immediate management, not to guide conservative observation.