In the context of HELLP syndrome, the class III (Tennessee classification) is distinguished from class I by which laboratory parameter threshold?
- A Class III: AST 40–70 IU/L; Class I: AST >70 IU/L
- B Class III: platelet count 100,000–150,000/mm³; Class I: <50,000/mm³ ✓
- C Class III: LDH 600–1000 IU/L; Class I: LDH >600 IU/L only
- D Class III: serum creatinine >1.1 mg/dL; Class I: creatinine normal
Correct answer: B. Class III: platelet count 100,000–150,000/mm³; Class I: <50,000/mm³
Explanation
The Tennessee (Martin) classification of HELLP syndrome grades severity by platelet count: Class III (50,000–100,000/mm³), Class II (50,000–100,000 with borderline haemolysis), and Class I (<50,000/mm³) with full haemolysis and AST >70 IU/L. Class I is the most severe and carries the highest maternal morbidity. The Mississippi classification by Sibai is a separate three-tier system also based primarily on platelet count. LDH threshold across classes is ≥600 IU/L for all classes in this system.
Reference: Williams Obstetrics, 26th ed.
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