HELLP Syndrome Classification Calculator
HELLP Syndrome Classification Calculator
Two published classifications that disagree: Mississippi grades three classes by platelet nadir, Tennessee calls it complete or partial. A laboratory reports against whichever the local unit uses, so this page keeps them separate rather than merging them into a scheme nobody published.
HELLP classification
Platelets + LDH + AST → classMississippi, platelet nadir 68 ×10⁹/L, LDH 780 U/L, AST 95 U/L, schistocytes on the film
The two systems, as published
Tennessee (Sibai) — complete: haemolysis (abnormal film, bilirubin ≥ 20.5 µmol/L, or LDH > 600 U/L) and AST ≥ 70 U/L and platelets < 100 ×10⁹/L; partial: one or two of the triad
- the platelet nadir
- Mississippi classifies on the lowest count at any point in the illness, not the admission count. A class assigned early is provisional and can only worsen
- inclusive bounds
- Mississippi’s bounds are inclusive at the top as Martin wrote them — ≤ 50, > 50 to ≤ 100, > 100 to ≤ 150 — which is why this page is an interpreter rather than a banded score. Some secondary sources render them as < 50, 50–100 and 100–150, which shifts a count of exactly 50 between classes
- class 3’s lower enzyme threshold
- 40 U/L rather than 70. This is easy to miss and it is the reason a set of results can be class 3 and yet fail the class 2 criteria on the enzyme alone
- LDH 600 U/L
- shared by both systems and method-dependent. LDH is a catalytic activity, so the number depends on the substrate direction, the buffer, the temperature and the assay formulation. A 600 U/L threshold is not transferable between methods without checking the reporting range
- where they disagree
- Mississippi accepts a platelet nadir up to 150 ×10⁹/L; Tennessee requires below 100. So every Mississippi class 3 case fails the Tennessee platelet criterion, and a case that is complete HELLP in Tennessee terms may be class 1 or class 2 in Mississippi terms. Neither maps onto the other
Worked example
Mississippi, platelet nadir 68 ×10⁹/L, LDH 780 U/L, AST 95 U/L, schistocytes on the film
Platelet nadir 68 — above 50, so not class 1; at or below 100, so within the class 2 range
LDH 780 ≥ 600 U/L → haemolysis criterion met
AST 95 ≥ 70 U/L → hepatic criterion met for classes 1 and 2
All three class 2 criteria satisfied → Mississippi class 2
The same sample under Tennessee: platelets 68 < 100, AST 95 ≥ 70, LDH 780 > 600 → complete HELLP
Both systems agree here, but they would not if the nadir were 130 — class 3 in Mississippi, and failing Tennessee's platelet criterion entirely
Mississippi triple-class system — Martin
| Class | Platelet nadir | AST or ALT | LDH |
|---|---|---|---|
| Class 1 | ≤ 50 ×10⁹/L | ≥ 70 U/L | ≥ 600 U/L |
| Class 2 | > 50 to ≤ 100 ×10⁹/L | ≥ 70 U/L | ≥ 600 U/L |
| Class 3 | > 100 to ≤ 150 ×10⁹/L | ≥ 40 U/L | ≥ 600 U/L |
Tennessee classification — Sibai
| Category | Haemolysis | AST | Platelets |
|---|---|---|---|
| Complete HELLP | All required: abnormal peripheral blood smear, bilirubin ≥ 20.5 µmol/L (1.2 mg/dL), LDH > 600 U/L | ≥ 70 U/L | < 100 ×10⁹/L |
| Partial HELLP | One or two elements of the triad — haemolysis, elevated liver enzymes, or thrombocytopenia — rather than all three | — | — |
The same sample, both systems
| Platelet nadir | Mississippi (LDH ≥ 600, enzymes met) | Tennessee (haemolysis and AST ≥ 70) |
|---|---|---|
| 40 ×10⁹/L | Class 1 | Complete HELLP |
| 68 ×10⁹/L | Class 2 | Complete HELLP |
| 95 ×10⁹/L | Class 2 | Complete HELLP |
| 130 ×10⁹/L | Class 3 (enzyme threshold 40 U/L) | Partial HELLP — the platelet criterion is not met |
| 170 ×10⁹/L | No class | Partial HELLP if haemolysis and AST are met |
Two classifications, and why merging them would be a mistake
HELLP syndrome — haemolysis, elevated liver enzymes, low platelets — has two published classifications, and they were built to answer different questions. Sibai’s Tennessee criteria ask whether the full triad is present: haemolysis, established by an abnormal peripheral blood film, a bilirubin at or above 20.5 µmol/L, or an LDH above 600 U/L; an AST at or above 70 U/L; and a platelet count below 100 ×10⁹/L. All three makes complete HELLP, one or two makes partial HELLP. Martin’s Mississippi triple-class system instead grades severity by the platelet nadir at any point in the illness — class 1 at or below 50 ×10⁹/L, class 2 above 50 up to 100, class 3 above 100 up to 150 — with an LDH at or above 600 U/L throughout and an AST or ALT at or above 70 U/L for the first two classes but only 40 U/L for the third.
The two do not map onto each other, and the place they diverge is the platelet count. Mississippi accepts a nadir up to 150 ×10⁹/L; Tennessee requires below 100. So every Mississippi class 3 patient fails the Tennessee platelet criterion and becomes, at most, partial HELLP — while a Tennessee complete HELLP patient could be class 1 or class 2 depending on how far the count eventually falls. A single merged scheme would have to pick one platelet threshold and one enzyme threshold, and in doing so it would silently reclassify patients relative to whichever system the local unit and the local literature use. That is why this page offers a selector and a comparison table rather than a consensus: the useful thing a calculator can do here is tell you what each published system says and where they part company, not invent a third.
Two features of Mississippi are worth drawing out because they change the answer. It classifies on the nadir, not on the admission count, so any class assigned during the illness is provisional and can only get worse — a woman who presents at 120 ×10⁹/L and falls to 45 is class 1, and the count commonly continues to fall for 24 to 48 hours after delivery before it turns. And class 3 carries a lower enzyme threshold than classes 1 and 2, which is easy to miss: a set of results can satisfy class 3 and fail class 2 on the transaminase alone. Class 3 is also not the reassuring category it can look like; it is better understood as a transitional phase that may be on the way up.
The LDH threshold deserves a specific caution, because 600 U/L is shared by both systems and is treated almost everywhere as a fixed number. It is not. LDH is a measure of catalytic activity rather than of a concentration, so the figure a laboratory reports depends on the method — on whether the lactate-to-pyruvate or the pyruvate-to-lactate reaction is measured, on the buffer, on the substrate concentrations and on the temperature. Two laboratories analysing the same serum can report materially different activities, both correctly. Check 600 against the reference range printed on your own report rather than treating it as a constant, and see the LDH unit converter for the relationship between U/L and µkat/L. Haemolysis in any case has other markers, and Sibai’s definition includes them: a blood film showing schistocytes, a raised bilirubin and a low haptoglobin can establish haemolysis before the LDH crosses any threshold.
Finally, the classification is not the diagnosis and neither is the diagnosis the management. HELLP sits inside the spectrum of severe pre-eclampsia and frequently presents with only mildly raised blood pressure and little or no proteinuria — see the pre-eclampsia laboratory criteria, where a platelet count below 100 ×10⁹/L is a severe feature on its own and proteinuria is not required. The differential also matters: acute fatty liver of pregnancy, thrombotic thrombocytopenic purpura and atypical haemolytic uraemic syndrome all overlap, and hypoglycaemia, marked jaundice, coagulopathy or neurological features should redirect the workup rather than confirm HELLP.
Frequently asked questions
What is the Mississippi classification of HELLP syndrome?
Three classes by platelet nadir: class 1 at or below 50 ×10⁹/L, class 2 above 50 up to 100, class 3 above 100 up to 150. All three require an LDH at or above 600 U/L; classes 1 and 2 require an AST or ALT at or above 70 U/L, while class 3 requires only 40 U/L. The class is assigned on the lowest count at any point in the illness, not on the admission value.
What is the Tennessee classification of HELLP syndrome?
Complete HELLP requires all three elements: haemolysis — an abnormal peripheral blood smear, a bilirubin at or above 20.5 µmol/L (1.2 mg/dL), or an LDH above 600 U/L — plus an AST at or above 70 U/L and a platelet count below 100 ×10⁹/L. Partial HELLP is one or two elements of the triad rather than all three, and can progress to complete HELLP over hours.
Why do the two classifications disagree?
Mainly on the platelet count. Mississippi accepts a nadir up to 150 ×10⁹/L and grades severity across three classes; Tennessee requires below 100 and asks only whether the triad is complete. So every Mississippi class 3 case fails the Tennessee platelet criterion. They answer different questions — one about severity and prognosis, one about whether the diagnosis is complete — so neither converts into the other.
Is the LDH threshold of 600 U/L reliable?
The threshold is real but it is method-dependent. LDH measures catalytic activity, not concentration, so the reported value depends on the reaction direction, buffer, substrate concentrations and temperature of the assay. Two laboratories can report materially different activities on the same serum. Check 600 U/L against the reference range on your own report rather than treating it as a universal figure.
Which class of HELLP is most dangerous?
Mississippi class 1, with a platelet nadir at or below 50 ×10⁹/L. In Martin’s original series approximately half of class 1 pregnancies had significant maternal morbidity, compared with 11% of pregnancies complicated by severe pre-eclampsia without HELLP. Tennessee provides no severity grading at all, which is one reason units that need a prognostic statement use Mississippi.
Can HELLP be diagnosed without proteinuria or severe hypertension?
Yes, and this is a common trap. HELLP frequently presents with only mildly raised blood pressure and little or no proteinuria. Neither classification requires either. Both ACOG and ISSHP diagnose pre-eclampsia without proteinuria when a severe feature is present, and a platelet count below 100 ×10⁹/L is one such feature on its own.
Related calculators
References
- Haram K, Svendsen E, Abildgaard U. The HELLP syndrome: clinical issues and management. A review. BMC Pregnancy Childbirth. 2009;9:8. doi:10.1186/1471-2393-9-8 — both classifications set out with their thresholds: Mississippi class 1 platelets ≤50 ×10⁹/L, class 2 >50 to ≤100, class 3 >100 to ≤150, with LDH >600 U/L and AST ≥70 U/L for classes 1 and 2 and AST ≥40 U/L for class 3; Tennessee complete HELLP requires abnormal blood smear, bilirubin ≥20.5 µmol/L, LDH >600 U/L, AST ≥70 U/L and platelets <100 ×10⁹/L, with partial HELLP being one or two elements of the triad.
- Martin JN Jr, Rinehart BK, May WL, Magann EF, Terrone DA, Blake PG. The spectrum of severe preeclampsia: comparative analysis by HELLP syndrome classification. Am J Obstet Gynecol. 1999;180(6):1373–1384 — classification by perinatal platelet nadir ≤150,000 cells/µL with AST ≥40 IU/L; approximately half of class 1 pregnancies exhibited significant maternal morbidity against 11% of severe pre-eclampsia without HELLP.
- Sibai BM. The HELLP syndrome (hemolysis, elevated liver enzymes, and low platelets): much ado about nothing? Am J Obstet Gynecol. 1990;162(2):311–316 — the Tennessee criteria.
- Aloizos S, et al. Diagnosis of HELLP Syndrome: A 10-Year Survey in a Perinatology Centre. Int J Environ Res Public Health. 2019;16(1):109. doi:10.3390/ijerph16010109 — Table 1 independently reproduces the Mississippi thresholds, including the inclusive upper bounds and the AST or ALT ≥40 IU/L threshold for class 3.
- American College of Obstetricians and Gynecologists. Gestational Hypertension and Preeclampsia: ACOG Practice Bulletin, Number 222. Obstet Gynecol. 2020;135(6):e237–e260 — a platelet count below 100,000/µL is a severe feature of pre-eclampsia in its own right, with or without proteinuria.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.