Approximately 2,600 cases of multiple myeloma (MM) were diagnosed in Brazil between 2013 and 2019, the monoclonal gammopathy of undetermined significance (MGUS), often asymptomatic, can progress to MM or other diseases, while Amyloidosis is characterized by the accumulation of free light chains (FLCs) in vital organs.

The objective of the study was to evaluate the accuracy of the Freelite® test compared to Serum Protein Electrophoresis (SPE) in detecting monoclonal gammopathies.

The research was carried out at the Clinical Hospital of the Botucatu Medical School, and included 203 patients treated in the Hematology, Nephrology, Internal Medicine, Rheumatology and Onco-Hematology sectors. The samples analyzed were subjected to the SPE and Freelite® tests, allowing the comparison of the methods. The data used for statistical analysis were the kappa and lambda indices, together with the K/L ratio in relation with the percentage value of beta and gamma globulins. Freelite® assays were performed using the Optilite® analyzer, and SPE assays using the G26 Easyfix automated analyzer.

The results showed that MM was the most prevalent diagnosis (82 out of 203 patients), followed by MGUS (14 out of 203). Amyloidosis was present in only one case. The gender distribution was balanced (49.75% females and 50.25% males). Regarding the effectiveness of the tests, using the Spearman statistic method, for patients with MM, Freelite® showed a statistically significant value only for the correlation between lambda (Freelite®) and gamma globulins (SPE), with a positive Spearman coefficient, that is, as one of the indices increases, the other tends to increase; In MM, SPE detected 24.3% of the cases with a monoclonal peak in gamma, however, Freelite® was able to detectc alterations in 25 cases where the SPE was within the reference values. In patients with MGUS, 28.6% had a monoclonal peak in Gamma; however, the statistical analysis indicated a correlation between Betaglobulins (SPE) in relation to Kappa and Lambda; however, the Spearman coefficient was a negative value, indicating a decreasing relationship.

Once a patient’s monoclonality has been defined, it is possible to monitor it based on the iFLC (Involved Free Light Chain), monitoring the results and progression of the disease according to its variation. A limitation of this study was the predominance of patients with MM under treatment during follow-up. This characteristic made it difficult to assess the efficacy of the tests in the initial diagnosis. Previous studies have already indicated that SPE has limited sensitivity to detect gammopathies, especially MM. The Freelite® test, by directly quantifying FLCs, increases diagnostic confidence and allows early detection. In conclusion, Freelite® has an adequate performance in monitoring monoclonal gammopathies due to its speed of analysis. The literature recommends the combined use of both methods to ensure a more sensitive and early diagnosis, contributing to a more effective clinical management of patients.