Role of Urine Tests in Multiple Myeloma Diagnosis and Monitoring

Diagnostic Role of Urine Testing

A 24-hour urine collection for protein electrophoresis and immunofixation is required to detect and characterize Bence Jones proteins (monoclonal free light chains) that may be excreted in the urine of multiple myeloma patients 1, 2
Random urine samples are insufficient and cannot replace a 24-hour urine collection, even when corrected for creatinine concentration 3
Urine protein electrophoresis should be performed on a concentrated sample from the 24-hour collection to improve detection sensitivity 3

Urine protein electrophoresis (UPEP) identifies the presence of a monoclonal protein as a homogeneous peak in the densitometer tracing 3
Urine immunofixation electrophoresis (UIFE) confirms the presence and type of heavy and light chains, even if there is no measurable protein or visible peak on electrophoresis 3
Quantification of the 24-hour urinary protein excretion helps determine the tumor burden and serves as a baseline for monitoring treatment response 3

Urine testing should be performed alongside serum protein electrophoresis, immunofixation, and serum free light chain assays for comprehensive evaluation 1

Serial measurements of urinary M-protein are used to assess treatment response and disease progression 4
Complete response criteria include negative immunofixation of both serum and urine 4
Partial response is defined as ≥50% reduction of serum M-protein and ≥90% reduction in 24-hour urinary light chain excretion or to <200 mg/24h 4

Failing to collect a complete 24-hour urine sample can lead to false-negative results 3
Inadequate concentration of urine samples may reduce sensitivity for detecting low levels of monoclonal proteins 3
Immunofixation should be performed even if there is no measurable protein or visible peak on electrophoresis to avoid false negatives 3

The National Comprehensive Cancer Network recommends that immunofixation electrophoresis (IFE) must be performed on both serum and urine as part of the initial diagnostic workup for all suspected multiple myeloma patients 5, 6
Serum immunofixation electrophoresis (SIFE) provides specific identification of the M-protein type by characterizing the heavy chain and light chain components 7, 8
SIFE should be combined with serum protein electrophoresis (SPEP) and serum free light chain (FLC) assay to achieve high sensitivity for screening multiple myeloma and related plasma cell disorders 5, 6

IFE is required to document complete response and stringent complete response according to International Myeloma Working Group criteria 5, 6
The FLC ratio must also be normal to document stringent complete response 7, 8, 6
Serial measurements using the same test method are essential to ensure accurate relative quantification and track disease progression 5, 6

Use the same testing method for serial studies to ensure accurate comparison of M-protein levels over time 5, 6
Do not substitute serum FLC assay for 24-hour urine protein electrophoresis in patients with measurable urinary M-proteins 7, 8, 6