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Biomarkers

α2-macroglobulin

A protein marker of liver fibrogenesis activity

Alpha-2-macroglobulin — a large blood plasma protein

Alpha-2-macroglobulin is a large plasma protein that works as a universal "trap" for enzymes (proteases) and as a carrier. It belongs to the globulin fraction of proteins.

Its greatest practical interest is in hepatology: its level rises in liver fibrosis, so alpha-2-macroglobulin is part of the non-invasive FibroTest index.

Reference ranges

The reference range depends on the lab; approximate values:

Normal (adults)≈ 1.3 – 3.0 g/L
High in liver fibrosiscontributes to the FibroTest index
Sharply highnephrotic syndrome (loss of small proteins)
In childrenphysiologically higher
Important: The value is rarely looked at in isolation. Its main worth is as a component of calculated liver-fibrosis indices.

What an elevated level means

A high alpha-2-macroglobulin has two main causes.

Liver fibrosis: as connective tissue builds up, its level rises — this is used in FibroTest and other indices. Nephrotic syndrome: the kidneys lose small proteins (albumin), while the large alpha-2-macroglobulin remains and relatively accumulates. Physiologically it is higher in children.

What a low level means

A low alpha-2-macroglobulin is rare and usually has no independent clinical significance. It can fall in acute inflammation of the pancreas (used up binding enzymes) and in some severe conditions.

How the test is done

Alpha-2-macroglobulin is measured in blood from a vein. It is rarely ordered on its own — more often it is part of a panel for calculating FibroTest together with haptoglobin, bilirubin, GGT and other measures.

What affects the value

  • Liver fibrosis — raises the level.
  • Nephrotic syndrome — raises it relatively.
  • Age — physiologically higher in children.
  • Acute pancreatitis — may lower it (used up).
  • Estrogens and pregnancy — raise it.
  • The lab method — affects the reference range.

Assess liver fibrosis

Alpha-2-macroglobulin is a component of FibroTest; assess your fibrosis risk:

FibroTest A non-invasive estimate of fibrosis stage — an alternative to biopsy Open FIB-4 (Liver Fibrosis) A first-line check for liver scarring, adjusted for age Open

Frequently asked questions

Why is alpha-2-macroglobulin tested?

Most often as part of a non-invasive assessment of liver fibrosis. Its level rises as fibrosis progresses, so it is part of the FibroTest index alongside haptoglobin, bilirubin and GGT. On its own, in isolation, it is rarely ordered.

Why does it rise in kidney disease?

In nephrotic syndrome the kidneys lose small proteins in the urine (albumin first of all), while the large alpha-2-macroglobulin is retained in the blood. Because of this its relative concentration rises.

What does alpha-2-macroglobulin do in the body?

It works as a universal "trap" for protease enzymes, neutralizing them, and also carries some signalling molecules. This makes it part of the blood's protective and regulatory systems.

Related terms

Liver fibrosis Scarring of the liver — the replacement of healthy tissue by connective tissue Haptoglobin A plasma protein; its level changes with liver fibrosis Globulins A fraction of plasma proteins; calculated as total protein − albumin Albumin The main plasma protein — a marker of protein status and liver function

Sources

  1. Alpha-2-macroglobulin and liver fibrosis (review). NCBI/PMC
  2. Non-invasive liver fibrosis markers (FibroTest). NCBI/PMC
  3. MedlinePlus (NIH) — Protein Electrophoresis
info
This content is educational and does not replace consultation with a physician. Reference ranges may vary depending on the laboratory and method — rely on the ranges stated on your own test report.
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