134 Serum globulin (GLB)

Serum globulins: immunoglobulins and other fractions, polyclonal vs monoclonal increase, antibody deficiency.

Serum globulins are all blood proteins other than albumin. They include transport and acute-phase proteins made by the liver (α₁- and α₂-globulins, β-globulins such as transferrin), and the immunoglobulins (γ-globulins, antibodies) produced by plasma cells. In a routine panel globulin is usually calculated as total protein minus albumin. A high value most often reflects chronic inflammation or infection. A very high or narrow-peaked increase can signal a monoclonal protein.

Blood proteinsImmunoglobulinsProtein electrophoresis

Adults≈ 20–35 g/L

Calculationtotal protein − albumin

A/G ratio≈ 1.1–2.0

Next test if highprotein electrophoresis

Figure 1. Electrophoresis separates the globulins into fractions. A broad γ increase suggests chronic inflammation (polyclonal); a narrow spike (dashed) suggests a monoclonal protein, as in myeloma or MGUS.

High globulins

Polyclonal (broad) increase: chronic infections (HIV, hepatitis B and C, tuberculosis, endocarditis), autoimmune diseases (lupus, rheumatoid arthritis, Sjögren syndrome), chronic liver disease and cirrhosis
Monoclonal (narrow) increase: monoclonal gammopathy of undetermined significance (MGUS), multiple myeloma, Waldenström macroglobulinaemia, some lymphomas
Dehydration (all proteins concentrated)

Low globulins

Low globulins, especially low γ-globulins, suggest antibody deficiency. This may be inherited (common variable immunodeficiency) or acquired: chronic lymphocytic leukaemia, myeloma (normal antibodies suppressed), nephrotic syndrome, protein-losing enteropathy, or immunosuppressive treatment. Recurrent bacterial infections, particularly of the chest and sinuses, are typical.

What to do

An unexplained high or low globulin should be investigated with serum protein electrophoresis and immunoglobulin levels. This is particularly important with anaemia, bone pain, high calcium, kidney problems or frequent infections.

References

Busher JT. Serum albumin and globulin. In: Walker HK, Hall WD, Hurst JW, eds. Clinical Methods: The History, Physical, and Laboratory Examinations. 3rd ed. Boston: Butterworths; 1990. Chapter 101. ncbi.nlm.nih.gov/books/NBK204
Rajkumar SV, Dimopoulos MA, Palumbo A, et al. International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma. Lancet Oncol. 2014;15(12):e538–e548. doi:10.1016/S1470-2045(14)70442-5

This article is for general information and does not replace a consultation with a doctor. Laboratory results must be interpreted by a physician together with symptoms and other tests.

Published on 12 May 2024