Novel extended reference range for serum κ/λ free light chain ratio in diagnosing monoclonal gammopathies in renal insufficient patients

Disease spectrum of abnormal serum free light chain ratio and its diagnostic significance

OBJECTIVE

To analyze the spectrum of abnormal serum free light chain ratio (sFLC κ/λ ratio), and to redefine the range of sFLC κ/λ ratio, so as to achieve hierarchical diagnosis of diseases with abnormal sFLC κ/λ ratio, resulting in the increased sensitivity and specificity in the diagnosis of monoclonal plasma diseases.

METHODS

Enrolled 1,340 patients with abnormal sFLC κ/λ ratio (<0.26 or >1.65) were grouped: (1) group A: malignant plasma diseases; (2) group B: monoclonal gammopathies of undetermined significance (MGUS); (3) group C: reactive plasma diseases. These patients were further divided by renal function eGFR <60 or >60 ml/min/1.73m2 to eliminate renal diseases influencing the results. Statistical analyses was performed by using SPSS 22 software.

RESULTS

When sFLC κ/λ ratio >3.49 and eGFR >60ml/min/1.73m2, the sensitivity and specificity of the diagnosis of malignant plasma diseases were 86.1% and 94.0%, respectively. When sFLC κ/λ ratio >2.89 and eGFR <60ml/min/1.73m2, the sensitivity and specificity of the diagnosis of malignant plasma diseases were 92.0% and 97.0%, respectively.

CONCLUSION

The sensitivity and specificity of the diagnosis of monoclonal plasma diseases can be significantly improved by redefining the cut-off value of sFLC κ/λ ratio and the renal function index of eGFR.

Role of serum free light chains in predicting HIV-associated non-Hodgkin lymphoma and Hodgkin's lymphoma and its correlation with antiretroviral therapy

A nested case-control study was performed within the Italian cohort of naïve to antiretroviral human immunodeficiency virus (HIV) patients (ICONA) cohort to evaluate the role of serum free light chains (sFLC) in predicting non-Hodgkin's lymphoma (NHL) and Hodgkin lymphoma (HL) in HIV-infected individuals. Of 6513 participants, 86 patients developed lymphoma and 46 of these (NHL, 30; HL, 16) were included in this analysis having stored prediagnostic blood. A total of 46 serum case samples matched 1:1 to lymphoma-free serum control samples were assayed for κ and λ sFLC levels and compared by using conditional logistic regression. Because the polyclonal nature of free light chains (FLCs) was the focus of our study, we introduced the k + λ sum as the measurement of choice and as the primary variable studied. κ + λ sFLC values were significantly higher in patient with lymphoma than in controls, especially when considering samples stored 0-2-year period before the lymphoma diagnosis. In the multivariable analysis, the elevation of sFLC predicted the risk of lymphoma independently of CD4 count, (odd ratio of 16.85 for k + λ sFLC >2-fold upper normal limit (UNL) vs. normal value). A significant reduction in the risk of lymphoma (odd ratio of 0.07 in model with k + λ sFLC) was found in people with low sFLC and undetectable HIV viremia lasting more than 6 months. Our analysis indicates that an elevated polyclonal sFLC is a strong and sensitive predictor of the risk of developing lymphomas, and it is an easy to measure biomarker that merits consideration for introduction in routine clinical practice in people with HIV.

Extended use of serum free light chain as a biomarker in lymphoproliferative disorders: a comprehensive review

Serum free light chain (sFLC) assays were shown to improve detection, management, and prognostication in plasma cell disorders. Recently, sFLC assays improved detection of M proteins when combined with standard methods of protein electrophoresis/immunofixation in patients with non-Hodgkin lymphoma/chronic lymphocytic leukemia (NHL/CLL). Incidence of abnormal sFLC ratio (sFLCr) varied from 0% to 36% and 29.7% to 59% in NHL and CLL, respectively. Increased sFLC levels or abnormal sFLCr predict shorter overall survival in early-stage CLL. Furthermore, abnormal sFLCr correlated with advanced disease stage and poorer outcome. In diffuse large B-cell lymphomas, increased sFLC was demonstrated as an independent, adverse prognostic factor for overall/event-free survival. Moreover, abnormal sFLCr can be a diagnostic tool in central nervous system lymphomas. Finally, the quantitative FLC assay has the potential to become a new, easily measured biomarker for predicting prognosis and enhanced detection in NHL/CLL. It may be used serially at follow-up evaluations to provide clues to relapse.

Elevated serum free light chains are associated with event-free and overall survival in two independent cohorts of patients with diffuse large B-cell lymphoma

PURPOSE

The serum free light chain (FLC) assay quantitates free kappa (κ) and free lambda (λ) immunoglobulin light chains. This assay has prognostic value in plasma cell proliferative disorders. There are limited data on serum FLC in B-cell malignancies.

PATIENTS AND METHODS

The association of pretreatment FLC with event-free survival (EFS) and overall survival (OS) in diffuse large B-cell lymphoma (DLBCL) was evaluated in 76 patients from the North Central Cancer Treatment Group trial N0489 (NCT00301821) and 219 patients from the University of Iowa/Mayo Clinic Specialized Program of Research Excellence Molecular Epidemiology Resource (MER). Published reference ranges were used to define an elevated FLC or an abnormal κ:λ FLC ratio.

RESULTS

Elevated FLC or abnormal κ:λ FLC ratio was present in 32% and 14% of patients, respectively. Patients with elevated FLC had an inferior OS and EFS in both cohorts compared with patients with normal FLC (N0489: EFS hazard ratio [HR], 3.06; OS HR, 3.16; both P < .02; MER: EFS HR, 2.42; OS HR, 3.40; both P < .001; combined EFS HR, 2.57; OS HR, 3.74; both P < .001). All associations remained significant for EFS and OS after adjusting for the International Prognostic Index (IPI). Abnormal κ:λ FLC ratio was modestly associated with outcome in the combined group (EFS HR, 1.61; OS HR, 1.67; both P = .07), but not in patients without corresponding elevated κ or λ. Elevated FLC was the strongest predictor of outcome in multivariable models with the IPI components.

CONCLUSION

Increased serum FLC is an independent, adverse prognostic factor for EFS and OS in DLBCL and warrants further evaluation as a biomarker in DLBCL.