Interpreting immunoglobulins and protein electrophoresis
Reading IgG, IgA and IgM levels, serum protein electrophoresis patterns, immunofixation, serum free light chains (including kidney-adjusted ratios) and urine studies, when to screen for a paraprotein, polyclonal versus monoclonal rises, and the artefacts and drug interference that mislead.
Tier 2Medical sciences concept
Written with AI assistance and fact-checked against the sources below. For exam study, not clinical decisions. How notes are made
At a glance
- Immunoglobulins (IgG, IgA, IgM) are measured by nephelometry. They tell you about quantity, not clonality.
- Serum protein electrophoresis (SPEP) separates proteins into albumin, alpha-1, alpha-2, beta and gamma bands. It detects a monoclonal band (paraprotein, M protein) and broad patterns such as polyclonal rise, nephrotic loss or hypogammaglobulinaemia.
- Immunofixation (IFE) types the band (heavy and light chain) and finds small ones. Serum free light chains (sFLC) find light chain-only disease.
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Sources
- MSAG clinical practice guidelines for newly diagnosed (transplant eligible and ineligible) and relapsed or refractory multiple myelomaAU/NZMedical Scientific Advisory Group to Myeloma Australia, 2026
- Tate J et al. Recommendations for standardized reporting of protein electrophoresis in Australia and New Zealand. Ann Clin Biochem 2012;49:242-56AU/NZAACB/RCPA working party, 2012
- Tate JR et al. Proposed addendum to 2012 recommendations for standardised reporting of protein electrophoresis in Australia and New Zealand. Clin Biochem Rev 2019;40:23-30AU/NZAustralasian Association of Clinical Biochemists, 2019
- RCPA Manual (immunoglobulins, protein electrophoresis, free light chains)AU/NZRoyal College of Pathologists of Australasia
- International Myeloma Working Group updated criteria for the diagnosis of multiple myeloma (Rajkumar SV et al. Lancet Oncol 2014;15:e538-48)International Myeloma Working Group, 2014 (current diagnostic criteria, November 2026)
- Long TE et al. Defining new reference intervals for serum free light chains in individuals with chronic kidney disease: results of the iStopMM study. Blood Cancer J 2022;12:133Blood Cancer Journal, 2022
- Wu J et al. Validation of free light chain reference intervals and their association with age and eGFR. Clin Chim Acta 2026;578:120494 (online July 2025)Clinica Chimica Acta, 2026
- Gustine JN et al. Serum IgM level as predictor of symptomatic hyperviscosity in patients with Waldenström macroglobulinaemia. Br J Haematol 2017;177(5):717-725British Journal of Haematology, 2017
- Last updated
- 14 November 2026
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