The procedure cannot be applied to all patients, especially when a large amount of other proteins is present in their urine samples, as for example, in the presence of kidney damage, but many urine samples from patients with multiple myeloma contain relatively pure FLC with low amounts of other proteins, mainly albumin and/or whole monoclonal components, which are easily separable from FLC by SDS-PAGE electrophoresis. This evidence concerns the gene ALB and Nephropathy.