What are the limitations of the ldh ast ratio?

While the ldh ast ratio is highly validated, it should not replace clinical judgment. OpiCalc provides the latest evidence-based limitations for the ldh ast ratio to ensure safe bedside use and optimal diagnostic accuracy.

How does the ldh ast ratio compare to other Hematology scores?

The ldh ast ratio is a gold-standard diagnostic tool. OpiCalc provides side-by-side clinical guidance to help clinicians choose the most specific evidence-based tool for their patient's presentation.

Is the ldh ast ratio free to use?

Yes. OpiCalc provides the ldh ast ratio completely ad-free and optimized for mobile bedside use, ensuring you can calculate medical risk swiftly and without distraction.

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LDH/AST Ratio (Haemolysis vs. Liver)

LDH/AST Ratio: A diagnostic tool for differentiating massive haemolysis from acute liver injury. LDH is 160x more abundant in RBCs than serum, while AST is only 40x.

Serum LDH (IU/L)

Serum AST (IU/L)

Guidelines & Evidence

Clinical Details

Section 1

When to Use

Differentiating hyperbilirubinaemia due to haemolysis from that due to acute liver injury (e.g., ischemic hepatitis).

Screening for thrombotic microangiopathy (TMA) in patients with multi-organ dysfunction.

Initial diagnostic workup of severe elevations in lactate dehydrogenase (LDH).

Patient Population

Patients with unexplained jaundice (indirect vs. direct hyperbilirubinaemia) and/or marked elevations in serum LDH.

Section 2

Formula & Logic

The Ratio Logic

LDH is abundant in red blood cells. AST is present in both liver and RBCs, but is much more specific to the liver than LDH. In massive haemolysis, LDH rises disproportionately to AST.

Interpretation

LDH/AST Ratio	Interpretation	Typical Condition
> 22.0	Strongly suggestive of Haemolysis	TTP, HUS, MAHA
< 15.0	Suggestive of Liver Injury	Shock Liver, Acute Viral Hepatitis
15.0 - 22.0	Indeterminate	Mixed picture or early presentation

Section 3

Pearls/Pitfalls

Ischemic Hepatitis (Shock Liver)

In shock liver, LDH and AST both rise rapidly (into the thousands), but the LDH/AST ratio typically remains < 10–12 because of the massive hepatic release of both enzymes.

TTP Warning

A very high LDH/AST ratio (> 25) in an ill patient with thrombocytopenia should raise immediate concern for Thrombotic Thrombocytopenic Purpura (TTP).

Section 4

Evidence Appraisal

Primary Score

Lactate dehydrogenase and aspartate aminotransferase as diagnostic tools for ischemic hepatitis.

Nathwani RA et al. • Digestive Diseases and Sciences. 2005;50(5):810-6.

View Source

Section 5

Literature

Pathophysiology

Red blood cells contain about 160 times as much LDH as serum, but only about 40 times as much AST. Liver cells contain vast amounts of both. This biological discrepancy forms the basis of the diagnostic ratio.

Last Comprehensive Review: 2026

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