Laboratory test

Alpha-1-Acid Glycoprotein (Orosomucoid)

Alpha-1-acid glycoprotein, also called orosomucoid or AGP (from the English alpha-1-acid glycoprotein), is a protein produced by the liver in response to damage to the body. It belongs to the family of positive acute phase proteins, the concentration of which increases during inflammation, infection, trauma, or active chronic disease. Its blood level is used to assess the intensity of an inflammatory syndrome and to monitor its evolution over time.

What is the role of alpha-1-acid glycoprotein?

AGP is a glycoprotein that is highly enriched in carbohydrates (approximately 45 % of its mass). It plays several important physiological roles within the inflammatory and immune response:

Immune response modulation: AGP exerts an anti-inflammatory effect by regulating immune cell activation and limiting excessive tissue damage
Drug binding: AGP binds to many basic or neutral drugs in the bloodstream, influencing their distribution and efficacy, notably antidepressants, antiarrhythmics, antipsychotics, and certain opioid analgesics.
Marker of systemic inflammation: its hepatic synthesis is strongly stimulated by pro-inflammatory cytokines such as interleukin-6 (IL-6) and TNF-alpha

In what contexts is this test prescribed?

The measurement of alpha-1-acid glycoprotein is requested in several clinical situations:

Indication	Objective
Inflammatory workup	Confirm and quantify an inflammatory syndrome in addition to CRP, ESR, and fibrinogen
Follow-up of a chronic inflammatory disease	Evaluate disease activity (rheumatoid arthritis, inflammatory bowel disease, lupus) and treatment response
Suspicion of severe infection	Contribute to the diagnosis of acute bacterial infection or sepsis in combination with other markers
Post-surgical or post-traumatic follow-up	Monitor the inflammatory response after major surgery or trauma
Pharmacokinetic evaluation	Understanding concentration variations of certain drugs related to P-gp in patients with abnormally high or low levels
Nutritional assessment	Interpret other proteins such as albumin or prealbumin, whose levels are influenced by the inflammatory state

How to interpret the results?

Reference values may vary slightly depending on the laboratory and the assay methods used. For guidance:

Result	Approximate value	Possible meaning
Normal	0.5 to 1.2 g/L	Absence of significant inflammatory syndrome
Elevated (moderate)	1.2 to 2.0 g/L	Moderate inflammation, infection, recent surgical or traumatic stress
High (marked)	Beyond 2.0 g/L	Severe inflammation, severe infection, active neoplasm, active autoimmune disease
Lowered	Below 0.5 g/L	Liver failure, nephrotic syndrome (proteinuria), severe malnutrition

ℹ️ Alpha-1-acid glycoprotein is rarely interpreted in isolation. It is part of a global inflammatory assessment that includes CRP, erythrocyte sedimentation rate (ESR), fibrinogen, and a complete blood count. It is the combination of these results, placed within the patient's clinical context, that guides the physician in their diagnosis.

What are the causes of elevated ALKP?

Acute or chronic bacterial infections (pneumonia, tuberculosis, endocarditis)
Chronic inflammatory diseases: rheumatoid arthritis, Crohn's disease, ulcerative colitis, systemic lupus erythematosus
Neoplasms: certain cancers cause an elevation of AGP as part of the tumor's inflammatory response.
Traumas, extensive burns, major surgeries
Myocardial infarction and other acute vascular events
Pregnancy, especially in the third trimester
High-dose corticosteroid or estrogen use

What causes a decrease in GGT?

Severe hepatocellular insufficiency: the liver can no longer synthesize enough proteins
Nephrotic syndrome: massive loss of proteins in the urine, including AGP
Severe protein-energy malnutrition
Exudative enteropathies with protein loss

What other tests are often associated?

CRP (C-reactive protein): inflammatory marker with a faster kinetic, rises and normalizes faster than AGP
Erythrocyte Sedimentation Rate (ESR): Global reflection of plasma inflammation
Fibrinogen: acute-phase protein involved in coagulation, often elevated in inflammatory contexts
Complete blood count (CBC): search for leukocytosis or anemia of inflammation
Albumin and prealbumin: negative acute phase proteins, whose levels decrease in inflammatory or malnourished contexts
Serum protein electrophoresis: allows visualization of the alpha-1 fraction where AGP migrates

AGP and drug pharmacokinetics

An often overlooked aspect of alpha-1-acid glycoprotein (AAG) is its role as a transporter for many medications. When its levels are high, a larger proportion of the drug becomes bound to AAG and is temporarily inactive. This can reduce the therapeutic effect and necessitate a dosage adjustment. This interaction notably affects certain antidepressants, antipsychotics, antiarrhythmics such as lidocaine and propafenone, as well as opioids like methadone. A physician or pharmacist may take AAG levels into account when an insufficient therapeutic response is observed despite seemingly adequate doses.

Consult at Clinique Omicron

If your doctor has prescribed a dosage of alpha-1-acid glycoprotein as part of an inflammatory assessment or monitoring of a chronic illness, the Clinique Omicron teams, at their service points in Quebec, can assist you in interpreting the results and guiding management according to your overall clinical picture.

The content of this page is provided for informational purposes only and is not intended to replace the advice of a qualified healthcare professional. Consult a physician for any symptoms, questions or decisions you may have regarding your health.

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