# Relevance of Prescribing Serum Immunofixation Electrophoresis in the Diagnosis of Monoclonal Gammopathies

## TL;DR

This study shows that immunofixation electrophoresis is more effective than serum protein electrophoresis for diagnosing monoclonal gammopathies and highlights the need for better test prioritization.

## Contribution

The study evaluates the diagnostic yield of immunofixation electrophoresis compared to serum protein electrophoresis in monoclonal gammopathy diagnosis and assesses prescription practices.

## Key findings

- Immunofixation electrophoresis detected monoclonal bands in all 79 patients with monoclonal gammopathies.
- Serum protein electrophoresis identified monoclonal peaks in only 69.6% of cases.
- Combined use of immunofixation electrophoresis and serum free light chain assays is the reference method for diagnosis.

## Abstract

Introduction

Immunofixation electrophoresis (IFE) is an immunoprecipitation technique that combines the electrophoretic separation of serum proteins with the identification of immunoglobulin heavy chains (IgG, IgA, IgM) and light chains (κ or λ) using targeted antisera. It is typically used as a complement to serum protein electrophoresis (SPE) when abnormal profiles, such as a monoclonal peak, are detected. IFE is a reference method for confirmation and phenotyping in the diagnosis of monoclonal gammopathies (MGs). This study aims to evaluate the diagnostic yield of IFE compared to SPE in patients with suspected MGs. It also seeks to assess whether current prescription practices for IFE, when used as a complement to SPE, align with clinical guidelines to minimize unnecessary testing.

Materials and methods

This retrospective study was conducted at the laboratory of Hôpital Universitaire International Cheikh Khalifa Ibn Zaid, Casablanca, Morocco, from January 2023 to January 2025. We collected 200 serum samples from patients with clinical suspicion of MG who underwent IFE performed on agarose gel using the HYDRASYS system (Sebia, Lisses, France).

Results

Among the 200 patients included in the study, 103 (51.5%) were men and 97 (48.5%) were women, resulting in a sex ratio of 1.06. The average age was 63 years. IFE was performed on all 200 samples and identified monoclonal bands in all 79 patients with MGs (100%), including the 55 cases (69.6%) that had monoclonal peaks detected by SPE. Thus, our study achieved a 100% detection rate of MGs by IFE, whereas SPE identified only 69.6%.

Discussion

IFE consistently demonstrates superior sensitivity to SPE. These data highlight the difficulty of interpreting electrophoretic profiles and the need to decide whether to follow up with IFE or simply monitor the patient. Although a normal SPE does not rule out the diagnosis of multiple myeloma (MM), emphasizing the need for IFE in cases of strong clinical suspicion, our series reveals that for a very large proportion of patients, SPE, IFE, and serum free light chain (FLC) assays were simultaneously requested by the clinician and all turned out negative. This underscores the importance of better prioritizing tests to avoid excessive and potentially unnecessary prescriptions for additional analyses. In all cases, direct communication between the biologist and the clinician is recommended.

Conclusion

While SPE is a useful and economical initial screening tool, IFE is essential for an accurate diagnosis of related monoclonal gammopathies due to its superior sensitivity and specificity. IFE, combined with complementary analyses such as serum FLC assays, currently constitutes the reference method for definitive identification.