Workup for Persistently Elevated Total Protein and Globulin
Order serum protein electrophoresis (SPEP) with immunofixation electrophoresis (SIFE) and 24-hour urine protein electrophoresis (UPEP) with urine immunofixation (UIFE) immediately, along with serum free light chain (FLC) assay to detect monoclonal proteins that may indicate plasma cell disorders, which carry significant mortality risk if undiagnosed. 1, 2
Initial Laboratory Testing
The following tests must be ordered simultaneously to avoid missing critical diagnoses:
SPEP with SIFE: Immunofixation is more sensitive than standard electrophoresis alone and can detect small monoclonal proteins that produce no visible spike on SPEP 2, 3. In patients with hypogammaglobulinemia and normal SPEP, immunofixation reveals monoclonal proteins in approximately 10% of cases 3.
24-hour urine collection with UPEP and UIFE: This cannot be replaced by random urine samples 1. Approximately 20% of multiple myeloma patients have measurable urinary monoclonal proteins, and 3% have nonsecretory disease detectable only through other methods 1.
Serum free light chain (FLC) assay with kappa/lambda ratio: This provides high sensitivity for screening plasma cell disorders and has prognostic value 1, 2. The FLC ratio is critical for risk stratification.
Quantitative immunoglobulins (IgG, IgA, IgM): Nephelometric quantitation helps identify which immunoglobulin is elevated and detects immune paresis 1.
Risk Stratification Based on FLC Ratio
The serum free light chain ratio determines urgency of further workup:
Markedly abnormal ratio (kappa/lambda >100 or <0.01): Proceed immediately to bone marrow biopsy regardless of immunofixation results, as this suggests high-risk plasma cell disorder 2.
Moderately abnormal ratio (>3.1 or <0.26) with normal renal function: This is highly suggestive of plasma cell disorder and warrants bone marrow evaluation 2.
Normal or mildly abnormal ratio: Continue with standard workup based on immunofixation results.
Additional Baseline Studies
Complete the following to assess for end-organ damage and tumor burden:
Complete blood count with differential: Anemia (hemoglobin <10 g/dL or >2 g/dL below normal) is a myeloma-defining event and predicts positive immunofixation 1, 3.
Comprehensive metabolic panel: Check serum calcium (≥11.5 mg/dL indicates hypercalcemia), creatinine (≥2 mg/dL indicates renal insufficiency), and albumin 1. Elevated creatinine predicts positive immunofixation in hypogammaglobulinemic patients 3.
Beta-2 microglobulin and LDH: These reflect tumor burden and are required for International Staging System prognostication 1.
Alpha-2 globulin/alpha-1 globulin ratio: An elevated ratio increases the odds of detecting a monoclonal protein by 2-fold 3.
Bone Marrow Evaluation (If Monoclonal Protein Detected)
If immunofixation or FLC ratio is abnormal, proceed with:
Bone marrow aspiration and biopsy: Required to quantify clonal plasma cells (≥10% defines myeloma) and assess for light chain-only myeloma or AL amyloidosis 1, 2.
Cytogenetic studies: Perform FISH analysis for del(13), t(4;14), t(14;16), del(17p), and 1q21 amplification for risk stratification 1, 2. These high-risk features determine prognosis and treatment approach.
Flow cytometry or immunohistochemistry: Confirms clonality of plasma cells 2.
Imaging Studies
Skeletal survey: Obtain posteroanterior chest, anteroposterior/lateral views of cervical/thoracic/lumbar spine, humeri, femora, skull, and anteroposterior pelvis to detect lytic lesions 1. Whole-body low-dose CT or MRI is preferred over plain radiographs when available 2.
MRI of spine and pelvis: Mandatory if solitary plasmacytoma is suspected; consider in smoldering myeloma as it detects occult lesions and predicts progression to symptomatic disease 1.
Cardiac Evaluation (If AL Amyloidosis Suspected)
If clinical features suggest amyloidosis (unexplained heart failure, LV wall thickness ≥14mm, low voltage ECG):
Cardiac workup: Echocardiography and cardiac biomarkers 2.
Tissue biopsy with Congo red staining: Renal biopsy with appropriate studies is necessary if amyloidosis is suspected in the context of plasma cell dyscrasia 1.
Common Pitfalls to Avoid
Do not rely on SPEP alone: Immunofixation is essential as small monoclonal proteins may not produce visible spikes 2, 3. Approximately 9.7% of patients with hypogammaglobulinemia and normal SPEP have positive immunofixation 3.
Do not substitute random urine for 24-hour collection: Random samples corrected for creatinine require further validation and cannot be recommended 1.
Do not skip FLC assay: It provides measurable disease in twice as many patients as urine M-spike and is required for documenting stringent complete response 1, 4.
Watch for biclonal gammopathies: These rare conditions require careful correlation of SPEP, densitometry tracing, and immunofixation to identify a second, less evident peak 5.