Monoclonal Protein Study, Random, Urine
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
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 use of a random urine specimen is sufficient for identifying the presence or absence of a monoclonal immunoglobulin, but a 24 hour specimen is preferred for quantitating and monitoring the abnormality.
See An Expanded Algorithm for the Laboratory Evaluation of Suspected Multiple Myeloma in Special Instructions and the Laboratory Approach to the Diagnosis of Amyloidosis algorithm in Special Instructions. Also see Diagnosis and Monitoring of Multiple Myeloma in Publications.
Diagnosing monoclonal gammopathies
A characteristic monoclonal band (M-spike) is often found in the urine of patients with monoclonal gammopathies. The initial identification of an M-spike or an area of restricted migration is followed by immunofixation to identify the immunoglobulin heavy chain and/or light chain.
Immunoglobulin free light chains as well as heavy chain fragments 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 multiple myeloma or macroglobulinemia.
The presence of a small amount of monoclonal light chain and proteinuria (total protein >3 g/24 hrs) that is predominantly albumin is consistent with primary systemic amyloidosis (AL) or light-chain deposition disease (LCDD).
Because patients with AL or LCDD may have elevated urinary protein without an identifiable M-spike, urine protein electrophoresis is not considered an adequate screen for these disorders and immunofixation is also performed.
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Monoclonal gammopathies are rarely seen in patients <30 years of age.
Hemolysis may cause a discrete band on protein electrophoresis, which will be negative on immunofixation.
Penicillin may split the albumin band.
Radiographic agents may produce an uninterpretable pattern.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
The following fractions, if present, will be reported as a percent of the total protein:
No reference values apply to random urine.
Clinical References Provides recommendations for further in-depth reading of a clinical nature
Kyle RA, Katzmann JA, Lust JA, Dispenzieri 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