|Values are valid only on day of printing.|
Identifying patients with a monoclonal M-spike
Urine proteins can be grouped into 5 fractions by protein electrophoresis:
The urine total protein concentration, the electrophoretic pattern, and the presence of a monoclonal immunoglobulin light chain may be characteristic of monoclonal gammopathies such as multiple myeloma, primary systemic amyloidosis, and light-chain deposition disease.
The following fractions, if present, will be reported as a percent of the total protein.
No reference values apply to random urines.
A characteristic monoclonal band (M-spike) is often found in the urine of patients with multiple myeloma (MM). The initial identification of an M-spike or an area of restricted migration should be followed by MPSU / Monoclonal Protein Study, 24 Hour, Urine, which includes immunofixation electrophoresis to identify the immunoglobulin heavy chain and/or light chain. Immunoglobulin heavy chain fragments as well as free light chains may be seen in the urine of patients with monoclonal gammopathies.
The presence of a monoclonal light chain M-spike of >1 g/24 hours is consistent with a diagnosis of MM or macroglobulinemia.
The presence of a small amount of monoclonal light chain and proteinuria (total protein >3 g/24 hours) that is predominantly albumin is consistent with primary systemic amyloidosis (AL) and light-chain deposition disease (LCDD). Because patients with AL and LCDD may have elevated urinary protein without an identifiable M-spike, urine protein electrophoresis is not considered an adequate screen for the disorder. MPSU / Monoclonal Protein Study, 24 Hour, Urine, which includes immunofixation electrophoresis, should be performed if the clinical suspicion is high.
Urine protein electrophoresis (PEL) alone is not considered adequate screening for monoclonal gammopathies. Patients suspected of having a monoclonal gammopathy may have a normal urine protein electrophoretic pattern, and these patients should have immunofixation electrophoresis (MPSU / Monoclonal Protein Study, 24 Hour, Urine) performed.
Random urine specimens may be sufficient for identifying monoclonal proteins, but 24 hour specimens should be used to quantitate and monitor urinary abnormalities.
Monoclonal gammopathies are rarely seen in patients <30 years of age.
Hemolysis may cause a discrete band on PEL, which will be negative on immunofixation.
Penicillin may split the albumin band.
Radiographic agents may produce an uninterpretable pattern.
1. Kyle RA, Katzmann JA, Lust JA, Dispenziei A: Clinical indications and applications of electrophoresis and immunofixation. In Manual of Clinical Laboratory Immunology. Sixth edition. Edited by NR Rose, et al. Washington, DC. ASM Press, 2002, pp 66-67
2. Kyle RA, Katzmann JA, Lust JA, Dispernzieri A: Immunochemical characterization of immunoglobulins. In Manual of Clinical Laboratory Immunology. Sixth edition. Edited by N.R. Rose, et al. Washington, DC. ASM Press, 2002, pp 71-91