Elimination of the need for urine studies in the screening algorithm for monoclonal gammopathies by using serum immunofixation and free light chain assays.
OBJECTIVE
To determine the relative diagnostic contribution of urine assays as part of the screening algorithm for monoclonal gammopathies.


METHODS
We identified 428 patients with a monoclonal gammopathy and monoclonal urinary protein at initial diagnosis of plasma cell dyscrasia who had also undergone serum immunofixation and serum free light chain quantitation within 30 days of diagnosis. The laboratory results for serum protein electrophoresis, serum immunofixation, serum free light chain, urine protein electrophoresis, and urine immunofixation were reviewed.


RESULTS
The patients had diagnoses of multiple myeloma, primary amyloid, monoclonal gammopathy of undetermined significance, smoldering multiple myeloma, solitary plasmacytomas, and other less frequently detected monoclonal gammopathies. All 428 had a monoclonal urine protein, 85.7% had an abnormal serum free light chain kappa/lambda ratio, 80.8% had an abnormal serum protein electrophoresis, and 93.5% had an abnormal serum immunofixation result. All 3 serum assays were normal in only 2 patients, 1 of whom had monoclonal gammopathy of undetermined significance (idiopathic Bence Jones proteinuria) and 1 whose urine sample contained an intact monoclonal immunoglobulin but whose serum and subsequent urine samples showed no evidence of a monoclonal gammopathy.


CONCLUSIONS
Discontinuation of urine studies and reliance on a diagnostic algorithm using only serum studies (protein electrophoresis, immunofixation, and free light chain quantitation) missed 2 (0.5%) of the 428 monoclonal gammopathies with urinary monoclonal proteins, and these 2 cases required no medical intervention.
Katzmann
Jerry A
JA
Division of Clinical Biochemistry and Immunology, Mayo Clinic College of Medicine, 200 First St SW, Rochester, MN 55905, USA. katzmann@mayo.edu
Dispenzieri
Angela
A
Kyle
Robert A
RA
Snyder
Melissa R
MR
Plevak
Matthew F
MF
Larson
Dirk R
DR
Abraham
Roshini S
RS
Lust
John A
JA
Melton
L Joseph
LJ
Rajkumar
S Vincent
SV
D000465:Algorithms; D003937:Diagnosis, Differential; D003951:Diagnostic Errors; D004586:Electrophoresis; D006801:Humans; D007147:Immunoglobulin Light Chains / Q000097:blood* / Q000652:urine; D010265:Paraproteinemias / Q000097:blood / Q000175:diagnosis* / Q000652:urine; D011507:Proteinuria; D016482:Urinalysis / Q000706:statistics & numerical data
D007147:Immunoglobulin Light Chains