Specimen Requirements for Serum Protein Electrophoresis (SPEP)
Serum Protein Electrophoresis (SPEP) requires a blood sample collected in a serum-separator tube or red-top tube, with 3 mL being the recommended volume for testing. 1
Collection and Handling Requirements
- Specimen type: Serum (not plasma or whole blood)
- Collection container: Serum-separator tube or red-top tube
- Minimum volume: 0.5 mL (though this may be insufficient for repeat testing)
- Recommended volume: 3 mL
- Processing: The specimen should be centrifuged with only serum sent for analysis
- Storage conditions:
- Up to 1 week when stored refrigerated
- Indefinite when stored frozen
Shipping and Transport
- Shipping temperature: Cold pack or frozen preferred; room temperature (20-25°C) is acceptable
- Delivery timeframe: Overnight delivery recommended
- Labeling: Patient's name and collection date must appear on specimen label 2
Quality Considerations
- Grossly hemolyzed, icteric, lipemic, or bacterially contaminated specimens cannot be tested properly and may yield inaccurate results
- Specimens with less than the recommended volume may be insufficient for repeat testing if needed 2
Clinical Context
SPEP is a critical test in the diagnostic workup of plasma cell disorders, particularly multiple myeloma. The National Comprehensive Cancer Network recommends SPEP as a first-line test for detecting monoclonal proteins (M-proteins) with a sensitivity of approximately 71% 1, 3.
Complementary Testing
For comprehensive evaluation, SPEP should be ordered alongside:
- Serum immunofixation electrophoresis (SIFE) to characterize any detected protein
- Serum free light chain (FLC) assay
- 24-hour urine collection for urine protein electrophoresis (UPEP) and immunofixation (UIFE) 1
Important Considerations
- Using consistent testing methods for serial monitoring is essential to ensure accurate relative quantification of M-proteins
- Approximately 3% of multiple myeloma patients have no detectable M-proteins on SPEP (nonsecretory disease), highlighting the importance of complementary testing 2, 1
- The accuracy and precision of SPEP decrease at lower M-protein concentrations, which may affect monitoring of minimal residual disease 4
By following these specimen collection and handling requirements, clinicians can ensure optimal results from SPEP testing for the diagnosis and monitoring of plasma cell disorders.