SFLC

Serum free light chains (SFLC) may be produced in excess by plasma cell dyscrasias such as multiple myeloma, Waldenstrom’s macroglobulinaemia, light chain deposition disease, amyloidosis & lymphocytic neoplasms. Measurement of SFLC & calculation of a kappa:lambda ratio can aid the diagnosis, prognosis & monitoring of these conditions. Up to 20% of multiple myelomas may be light chain-only and undetectable on serum protein electrophoresis.

When multiple myeloma or other plasma cell dyscrasias are suspected serum protein electrophoresis, immunoglobulins and urine BJP should be requested. At the present time, screening by SFLC are not routinely available in Scotland. SFLC should be used in conjunction with serum protein electrophoresis and immunoglobulins for diagnosis^1,2,3. If SFLC are unavailable, request urine BJP (Bence Jones Protein)⁵.

Patients with MGUS (monoclonal gammopathy of undetermined significance) who are being followed up in primary care do not require routine SFLC monitoring unless symptoms escalate or new symptoms develop or advised to by secondary care³.

• Patients with active or smouldering disease (including amyloidosis, non-secretory myeloma and light chain only myeloma) will be followed up by Haematologists according to local management protocols. If no local guidelines available, repeat SFLC analysis is not required within 3 months⁴.
• Patients with MGUS should have serum protein electrophoresis, FBC, U&E’s & calcium monitored as per local guidelines – monitoring by SFLC is not required routinely.

Please note local management protocols may vary & local guidelines should be followed.

1. National Institute for Health and Care Excellence. Myeloma: diagnosis and management [Internet]. [London]: NICE; 2016 [updated 2018 Oct; cited 2022 Oct 04]. (NICE guideline [NG35]). Available from: https://www.nice.org.uk/guidance/ng35
2. Sive J, Cuthill K, Hunter H, Kazmi M, Pratt G, Smith D, et al. Guidelines on the diagnosis, investigation and initial treatment of myeloma: a British Society for Haematology/UK Myeloma Forum Guideline. British Journal of Haematology. 2021;193(2):245–68. Available from: https://onlinelibrary.wiley.com/doi/10.1111/bjh.17410 DOI: 10.1111/bjh.17410
3. Dispenzieri A, Kyle R, Merlini G, Miguel JS, Ludwig H, Hajek R, et al. International Myeloma Working Group guidelines for serum-free light chain analysis in multiple myeloma and related disorders. Leukemia. 2009 Feb;23(2):215–24. Available from: https://www.nature.com/articles/leu2008307 DOI: 10.1038/leu.2008.307
4. Lang T., Croal B. National minimum retesting intervals in pathology [Internet]. 2nd ed. The Royal College of Pathologists; 2021 [cited 2022 Oct 04]. Available from: https://www.rcpath.org/resourceLibrary/g147-minimum-retesting-intervals-in-pathology.html
5. Myeloma Diagnostic Tool: Guidance for Primary Care [Internet]. Myeloma UK; 2020 [cited 2020 Oct 04]. Available from: https://academy.myeloma.org.uk/wp-content/uploads/2020/08/GP-Myeloma-Diagnostic-Tool-MA.pdf