Free Light Chains, C3, Rheumatoid Factor Update

Effective Dec 13th, Main Line Health Labs will start performing serum Kappa/Lambda free light chains, Complement C3, C4, Rheumatoid factors, using Optilite instrument instead of Beckman Immage. Optilite instrument utilize immunoprecipitation method instead of conventional Nephelometry method for testing. As a result of this, reference range for Kappa free light chain will change to 7.9 to 37.77 mg/dl from 3.3 to 19.4 mg/dl. Lambda free light chain reference range will not change. The reference Kappa/Lambda ratio will be 0.64-1.83. Furthermore, light chain assays between immunoprecipitation method and Nephelometry method are not comparable and cannot be used interchangeably, therefore your patients’ results for Kappa will change with a positive bias of 39%. We recommend setting up a new baseline for patients that are being followed for plasma cell dyscrasia.

Complement C3 will be measured using C3C, a subunit of complement C3 and reference range for complement C3 will be 72-185 mg/dl.

Rheumatoid factor will be IgM antibody instead of current IgG antibody and results for IgM antibody with Optilite and IgG antibody with Immage are not comparable.

If you have any questions, please call Dr. Bhagat at 484-476-3521


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