Thread by @aishaikh

Workup for detection of Monoclonal Immunoglobulin (MIg) in patients with Monoclonal Gammopathy of Renal Significance (MGRS)

(Talk by Dr. Frank Bridoux at the Kidney Week)
#Onconephrology #MGRS

Workup for detection of Monoclonal Immunoglobulin

1. Find the circulating monoclonal Ig:

-SPEP & UPEP to quantify the Monoclonal (M) spike

-Serum & Urine Immunofixation to identify the monoclonal Ig & also to monitor response to Rx

2. Serum Free Light Chain Assay to identify free light chains & to monitor hematological response to Rx in Light Chain-associated kidney disorders

There are 2 different LC assays: Binding site & N-Latex assay
-Use same assay to follow LC levels

3. If the Clone cannot be detected in serum or urine by SPEP/IF, UPEP/IF, sFLC assay then do Immunoblot Analysis of the serum & urine as it can detect small amounts of monoclonal immunoglobulins i.e. it is more sensitive

4. Mass Spectrometry Assays are very sensitive in detecting monoclonal light chains & MS assay may replace Immunofixation

-MS assays also distinguish b/w therapeutic antibodies (which may be picked on Immunofixation: False +) from endogenous M-proteins

5. Determine the nature of the detected clone

Bone Marrow Aspiration/Biopsy:

-Immunohistochemistry & Flow cytometry to analyze lymphocyte & plasma cell markers
-FISH panel for cytogenetic abnormalities
-Molecular Biology to look for mutations

6. If Clone is detected on Bone Marrow aspirate/biopsy & nature of the clone has been determined then determine tumor burden: CRAB criteria/CT/PET/MRI

7. If Clone is not detected on Bone marrow aspirate/biopsy:

-Flow cytometry of blood lymphocytes to detect small circulating clone
-Whole body imaging to detect localized plasmacytoma/low grade B-cell lymphoma

8. There are newer techniques that can be used for detection of small clones in patients with MGRS

-Next generation flow cytometry
-RNA-based Immunoglobulin Repertoire Sequencing (RACE RepSeq)

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