B-307 Comparative studies on serum quantitative immunoglobulin assay and serum protein electrophoresis for the diagnosis of multiple myeloma
Authors: Shrestha S , Osa-Andrews B 
Published: October 2024

Abstract

Background
Various clinical laboratory tests are valuable in enhancing the diagnosis of monoclonal gammopathy. The nephelometric-based serum quantitative immunoglobulin test provides great utility to understand the magnitude of antibody-mediated responses and is useful in interpreting Serum protein electrophoresis (SPEs). In clinical practice, several (SPEs) are ordered without a preliminary order of serum quantitative immunoglobulins but pathologists can and do order the test for comparison. However, there is seldom any data in the literature describing the correlative relationship between the two tests. It is therefore imperative to create an evidenced-based system of test-ordering for the laboratory investigation of the presence of monoclonal protein. The goal of the project is to compare the results of quantitative serum immunoglobulin assay and SPE in order to determine their concordance.

Methods
In this preliminary phase of the project, retrospective results of quantitative serum immunoglobulin assay and SPEs that were performed simultaneously were retrieved from the electronic medical records. The span of data extended to the past 1 year. If there is an additional immunofixation (IFE) order associated with the SPE, the IFE report was also retrieved for further comparison. Based on the etiology of multiple myeloma, results of calcium, red blood cell count and creatinine were also pooled and analyzed. Results of free light chain assay and associated kappa-lambda ratios were also obtained. All the data obtained were entered into and filtered in excel spreadsheet program and subsequently analyzed with GraphPad prism.

Results
1000 patient results were analyzed, of which 404 were males and 596 were females. 200 of the patients had either SPE or quantitative immunoglobulin performed which had the following age demographic; 23 were between 18-39 years, 52 were 40-59 years and 125 were 60-89 years. This data suggests geriatric population are more likely to be seen for multiple myeloma suspicion. There were 60 concurrent orders. Of this, there was 65.5% agreement between the serum quantitative immunoglobulin assay and SPE or IFE while 34.5% showed a mismatch. 26% of the orders for quantitative immunoglobulins assay had no follow-up SPE. A high Kappa/lambda ratio was concordant with a positive SPE 83% of the time. But only 66% of normal kappa/lambda ratio matched a normal SPE.

Conclusions
Here, we have shown that in addition to the kappa/lambda ratio, the quantitative immunoglobulins test has a considerable agreement with SPE and may be an important preliminary test. The test could be useful to rule out monoclonal gammopathy, confirm polyclonal pattern or embolden a normal SPE interpretation. The present research will have a direct impact on the diagnosis and monitoring of monoclonal gammopathy and enhance appropriate test utilization. The research will improve the development of a better ordering policy for laboratory operations with respect to the work up of multiple myeloma. As more data is unraveled, better understanding will be gained into the relationship between quantitative immunoglobulin and SPE for better patient care.