Pre-Eclampsia Laboratory Criteria Interpreter
Pre-Eclampsia Laboratory Criteria Interpreter
The laboratory half of the diagnosis only — platelets, creatinine, transaminases and proteinuria — against ACOG or ISSHP, because the two bodies disagree on three of the four thresholds. Blood pressure belongs to the diagnosis too, and this page does not pretend to make it.
Pre-eclampsia laboratory criteria
4 analytes × 2 criteria setsACOG criteria, platelets 92 ×10⁹/L, creatinine 84 µmol/L, no doubling, ALT 28 U/L against a laboratory limit of 33, protein:creatinine ratio 18 mg/mmol
The laboratory criteria, side by side
- platelets
- ACOG: below 100,000 per microlitre (100 ×10⁹/L), a severe feature. ISSHP: below 150,000 per microlitre, among the haematological complications. A 50% difference in the threshold
- creatinine
- ACOG: greater than 1.1 mg/dL (97.2 µmol/L), or a doubling of the serum creatinine, in the absence of other renal disease. ISSHP: at or above 90 µmol/L, which it gives as 1 mg/dL
- transaminases
- ACOG: elevated to twice normal — a multiple of your laboratory’s own upper limit. ISSHP: ALT or AST above 40 IU/L, an absolute figure. In most laboratories ISSHP fires first
- proteinuria
- both: 300 mg or more per 24 hours, or a protein:creatinine ratio of 30 mg/mmol (0.3 mg/mg) or more. ACOG permits a dipstick of 2+ only where no quantitative method is available
- what this page is not
- the blood-pressure criteria are part of the diagnosis: 140 systolic or 90 diastolic on two occasions at least four hours apart after 20 weeks, with the severe range at 160 or 110. So are pulmonary oedema, headache, visual symptoms and epigastric pain. This page covers the laboratory limb and nothing else
Worked example
ACOG criteria, platelets 92 ×10⁹/L, creatinine 84 µmol/L, no doubling, ALT 28 U/L against a laboratory limit of 33, protein:creatinine ratio 18 mg/mmol
Platelets 92 < 100 ×10⁹/L → severe feature met
Creatinine 84 µmol/L, below the ACOG threshold of 97.2 (1.1 mg/dL), and no doubling recorded
ALT 28 against twice the laboratory limit of 66 → not met
Protein:creatinine ratio 18 mg/mmol, below 30 → no proteinuria
One severe feature is enough: with new-onset hypertension this is pre-eclampsia with severe features, and the absence of proteinuria is irrelevant
Note what the same sample would do under ISSHP — the platelet criterion there is 150, so it would be met even more readily, while the creatinine at 84 would still be below the 90 threshold
ACOG against ISSHP, threshold by threshold
| Criterion | ACOG Practice Bulletin 222 | ISSHP 2018 | Same? |
|---|---|---|---|
| Platelet count | Below 100,000/µL (100 ×10⁹/L) | Below 150,000/µL (150 ×10⁹/L) | No |
| Serum creatinine | Greater than 1.1 mg/dL (97.2 µmol/L), or doubling | At or above 90 µmol/L (1 mg/dL) | No |
| Transaminases | Twice the laboratory’s upper limit of normal | ALT or AST above 40 IU/L | No |
| Proteinuria, 24-hour | 300 mg or more | 300 mg or more per day | Yes |
| Proteinuria, ratio | Protein:creatinine 0.3 mg/mg or more | 30 mg/mmol (0.3 mg/mg) or more | Yes |
| Proteinuria, dipstick | 2+, only if no quantitative method available | A negative dipstick can usually be accepted; quantify otherwise | Broadly |
| Proteinuria required? | No — severe features diagnose without it | No — “present in about 75% of cases” | Yes |
| Pulmonary oedema | A severe feature | Not in the list as quoted | No |
| Uteroplacental dysfunction | Not a criterion | Fetal growth restriction, abnormal umbilical artery Doppler, stillbirth | No |
Where the numbers live in each convention
| Analyte | Threshold | Other convention | Converter |
|---|---|---|---|
| Platelets | 100 ×10⁹/L (ACOG) | 100,000 per µL | Platelet count |
| Platelets | 150 ×10⁹/L (ISSHP) | 150,000 per µL | Platelet count |
| Creatinine | 97.2 µmol/L (ACOG) | 1.1 mg/dL | Creatinine |
| Creatinine | 90 µmol/L (ISSHP) | 1.0 mg/dL | Creatinine |
| ALT / AST | 40 IU/L (ISSHP) | 0.67 µkat/L | ALT · AST |
| Urine protein:creatinine | 30 mg/mmol | 0.3 mg/mg | Protein:creatinine ratio |
The laboratory limb, and what it cannot do alone
The single most consequential change in the diagnosis of pre-eclampsia over the past decade is that proteinuria stopped being required. Both ACOG and ISSHP now diagnose pre-eclampsia in a woman with new-onset hypertension after twenty weeks and no protein in her urine at all, provided there is evidence of maternal organ dysfunction — a platelet count below threshold, a rising creatinine, transaminases above threshold, pulmonary oedema, or the neurological features. ISSHP says it in as many words: proteinuria is not required for a diagnosis of pre-eclampsia, but is present in about seventy-five per cent of cases. ACOG’s diagnostic box carries the same logic in the phrase “or in the absence of proteinuria, new-onset hypertension with the new onset of any of the following”. A quarter of cases will be missed by anyone still waiting for a dipstick, and the cases missed are not the mild ones — HELLP syndrome routinely presents without significant proteinuria.
What the two bodies do not agree on is where the laboratory thresholds sit, and the disagreement is larger than it looks. ISSHP counts thrombocytopenia from below 150,000 per microlitre; ACOG’s severe feature is below 100,000 — a fifty per cent difference, and the single widest gap between them. ISSHP takes any ALT or AST above 40 IU/L; ACOG requires transaminases at twice the reporting laboratory’s own upper limit, which in a laboratory quoting 33 U/L means 66 U/L. ISSHP’s creatinine threshold is 90 µmol/L and ACOG’s is above 1.1 mg/dL, which is 97.2 µmol/L. Only proteinuria is common ground, where 300 mg per twenty-four hours and a protein:creatinine ratio of 30 mg/mmol — the same thing as 0.3 mg/mg — are shared. Beyond the numbers the two lists differ in composition: ACOG counts pulmonary oedema, ISSHP’s list as published does not, and ISSHP counts uteroplacental dysfunction including fetal growth restriction and abnormal umbilical artery Doppler, which ACOG does not. So a woman can meet one definition and not the other on identical results, and two published cohorts described with the same word are not describing the same patients.
Two features of the criteria are worth drawing out because they are easy to under-weight. The renal criterion has a doubling arm as well as an absolute one, and the doubling arm does most of the work in young women: glomerular filtration rises in normal pregnancy and creatinine falls with it, so a booking value of 45 µmol/L can double to 90 while still sitting inside a non-pregnant reference interval. A creatinine that has doubled is a severe feature regardless of where it has doubled to. And the hepatic criterion in ACOG’s formulation is a ratio, not a value, which is why this page asks for your laboratory’s upper limit rather than assuming one — methods and sex-specific ranges differ enough that assuming 40 would silently convert an ACOG assessment into an ISSHP one.
The important limitation is what this page leaves out. Pre-eclampsia is a diagnosis of hypertension plus something else, and the hypertension is not an input here: systolic 140 or diastolic 90 on two occasions at least four hours apart after twenty weeks in a woman previously normotensive, with the severe range at 160 or 110. Nor are the clinical severe features, which are a substantial part of the box — pulmonary oedema, new-onset headache unresponsive to medication and not accounted for otherwise, visual symptoms, and severe persistent right upper quadrant or epigastric pain. None of those is measurable in a laboratory and any of them can precede the biochemistry. So read the output above as an answer to one question — is a laboratory criterion met — and not as a diagnosis. Where the platelet count and the transaminases move together, classify on the HELLP criteria. Where the question is whether pre-eclampsia can be ruled out over the next week, the sFlt-1/PlGF ratio answers that specific question better than any of these four analytes.
Frequently asked questions
Is proteinuria required to diagnose pre-eclampsia?
No. Both ACOG and ISSHP diagnose pre-eclampsia in a woman with new-onset hypertension after 20 weeks and no proteinuria, provided there is evidence of maternal organ dysfunction — thrombocytopenia, renal insufficiency, impaired liver function, pulmonary oedema or neurological features. ISSHP states that proteinuria is present in about 75% of cases, so a quarter are missed by waiting for it.
What platelet count defines pre-eclampsia with severe features?
This is where the two bodies disagree most. ACOG’s severe-feature threshold is a platelet count below 100,000 per microlitre, that is below 100 ×10⁹/L. ISSHP counts thrombocytopenia from below 150,000 per microlitre among the haematological complications that make gestational hypertension into pre-eclampsia. A count of 130 ×10⁹/L meets ISSHP and not ACOG.
What creatinine level counts as renal insufficiency in pre-eclampsia?
ACOG uses a serum creatinine greater than 1.1 mg/dL, which is 97.2 µmol/L, or a doubling of the serum creatinine, in the absence of other renal disease. ISSHP uses 90 µmol/L or above. The doubling arm matters because pregnancy lowers creatinine, so a woman who started at 45 µmol/L can double to 90 while still appearing normal against a non-pregnant interval.
How high do transaminases need to be?
ACOG requires liver transaminases elevated to twice normal, meaning twice the reporting laboratory’s own upper limit — 66 U/L in a laboratory quoting 33. ISSHP uses an absolute figure, ALT or AST above 40 IU/L, with or without right upper quadrant or epigastric pain. In most laboratories the ISSHP threshold is reached first.
Can a dipstick be used for proteinuria?
ACOG permits a dipstick reading of 2+ but specifies that it is used only if other quantitative methods are not available. A protein:creatinine ratio of 30 mg/mmol or 0.3 mg/mg, or 300 mg or more in a 24-hour collection, is the proper measurement. ISSHP notes that a negative dipstick can usually be accepted without further quantification at that time.
Does this page diagnose pre-eclampsia?
No, and it does not try to. Pre-eclampsia requires hypertension — 140 systolic or 90 diastolic on two occasions at least four hours apart after 20 weeks, severe range 160 or 110 — which is not an input here. Several severe features are clinical rather than laboratory: pulmonary oedema, new-onset headache unresponsive to medication, visual symptoms and severe epigastric pain. This page covers the laboratory limb only.
Related calculators
References
- American College of Obstetricians and Gynecologists. Gestational Hypertension and Preeclampsia: ACOG Practice Bulletin, Number 222. Obstet Gynecol. 2020;135(6):e237–e260 — Box 2 diagnostic criteria: platelet count less than 100,000/µL; serum creatinine greater than 1.1 mg/dL or a doubling of the serum creatinine; liver transaminases to twice normal; proteinuria 300 mg or more per 24 hours, protein/creatinine ratio 0.3 mg/dL or more, or dipstick 2+ “used only if other quantitative methods not available”.
- Brown MA, Magee LA, Kenny LC, et al. Hypertensive Disorders of Pregnancy: ISSHP Classification, Diagnosis, and Management Recommendations for International Practice. Hypertension. 2018;72(1):24–43. doi:10.1161/HYPERTENSIONAHA.117.10803 — “Proteinuria is not required for a diagnosis of pre-eclampsia but is present in about 75% of cases”; creatinine ≥90 µmol/L; ALT or AST >40 IU/L; platelet count below 150,000/µL; PCr ratio ≥30 mg/mmol (0.3 mg/mg).
- Khedagi AM, Bello NA, et al. The evolution of the diagnostic criteria of preeclampsia-eclampsia. Am J Obstet Gynecol. 2022 — comparison of ACOG 2018 and ISSHP 2018 organ-dysfunction definitions: platelets <100,000/µL vs 1.1 mg/dL vs ≥90 µmol/L; transaminases ≥twice normal vs ≥40 IU/L.
- Zeisler H, Llurba E, Chantraine F, et al. Predictive value of the sFlt-1:PlGF ratio in women with suspected preeclampsia. N Engl J Med. 2016;374(1):13–22.
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.