Which assay is recommended for detecting serum-free light chains in multiple myeloma patients?

The assay recommended for detecting serum-free light chains in multiple myeloma patients is nephelometry. This method measures the concentration of free light chains in serum by allowing the formation of immune complexes when antibodies specific to light chains are added to the sera. The resulting complexes scatter light in a way that is quantifiable, providing accurate measurements of kappa and lambda light chains.

Nephelometry is particularly useful in this context because it allows for the differentiation of free light chains from other proteins present in the serum, thus providing a more specific assessment of the light chain levels. This is critical in the diagnosis and monitoring of multiple myeloma, as abnormal levels of kappa or lambda light chains can indicate the presence and severity of the disease.

Other assays, while useful in different contexts, may not provide the specificity or sensitivity needed for light chain detection. For example, serum protein electrophoresis measures all serum proteins and can indicate the presence of monoclonal proteins (which include light chains), but it does not separate light chains sufficiently for accurate quantitation. Urine immunofixation detects intact monoclonal proteins in urine but does not measure serum-free light chains effectively. ELISA can be utilized in detecting various immunoglobulins, including light chains