Kidney disease and plasma cell dyscrasias: ambiguous cases solved by serum free light chain dimerization analysis.

BACKGROUND: Plasma cell dyscrasias (PCD) comprise a wide spectrum of disorders, which may adversely affect the kidney. However, in some PCD cases associated with kidney disease, the routine laboratory tests may be incapable to determine precisely the form of PCD, i.e., benign or malignant. Moreover, the kidney biopsy needed for precise diagnosis may be risky or declined. To overcome these limitations, we have developed and reported a new non-invasive technique based on serum free light chains (FLC) monomer (M) and dimer (D) pattern analysis (FLC MDPA), which allowed differentiation between malignant and benign PCD forms. The objective of our retrospective study was to demonstrate the utility of FLC MDPA in solving ten puzzling PCD cases complicated with kidney disease (patients 1-10). METHODS: Ten patients with uncertain form of PCD or with a questionable response to treatment were studied. In addition to routine laboratory tests and clinical evaluation of the PCD patients, our previously developed FLC MDPA in sera and biochemical amyloid typing in biopsy tissues were applied. RESULTS: The FLC MDPA aided the diagnosis of the PCD underlying or accompanying the kidney disease in patients 1-5, and helped to interpret properly the response to treatment in patients 1, 6-10. The FLC MDPA findings were confirmed by a biochemical analysis of tissue amyloid deposits and subsequently by the outcome of these patients. CONCLUSIONS: FLC MDPA is a non-invasive diagnostic test useful in the management of ambiguous cases of PCD associated with kidney disease.

The use of serum free light chain dimerization patterns assist in the diagnosis of AL amyloidosis.

The discrimination between benign and malignant forms of plasma cell dyscrasia (PCD) is often difficult. Free light chain monomer-dimer pattern analysis (FLC-MDPA) may assist in solving this dilemma and distinguish between AL amyloidosis and benign PCD. Serum samples of patients with AL amyloidosis and benign PCD were analysed in a blinded manner. Quantitative Western blotting was performed to estimate dimerization and clonality indices, and thereby determine the source of the tested samples, as derived either from benign or malignant PCD. The findings obtained by the FLC-MDPA were compared with the actual diagnosis. Of 37 samples from patients with active AL amyloidosis, 34 (91·9%) fulfilled dimerization criteria for diagnosis of AL amyloidosis. Of the 45 samples from patients with benign PCD, 10 (21·2%) tested falsely positive or gave an inconclusive result. Thus, the sensitivity of the analysis was 92·5% with a remarkable negative predictive value of 91·9%. In addition, of 20 patients who were in complete or very good partial remission, only one tested positive. By multivariate analysis, FLC-MDPA was the best independent marker predicting AL amyloidosis (odds ratio of 84). The FLC-MDPA offers a highly effective tool in the diagnostic assessment of patients with PCD.

Search for new biomarkers of pediatric multiple sclerosis: application of immunoglobulin free light chain analysis.

BACKGROUND: Identifying new biomarkers is needed to overcome the diagnostic difficulties of pediatric multiple sclerosis (MS). Recently, we developed a new technique including CSF analysis of free light chain (FLC) monomers and dimers, which can improve diagnosis of adult MS. The present study has been designed to evaluate the utility of our technique for MS diagnosis in children. METHODS: Patients with MS (n=21) and non-MS demyelinating or inflammatory neurological disorders (n=35) participated in the study. MS diagnosis was based on clinical and magnetic resonance imaging (MRI) findings. Western blot analysis was applied to examine FLC in the patients' CSF and serum. FLC indices for FLC monomer and dimer levels and κ/λ ratios were estimated. The samples were also analyzed by oligoclonality test. RESULTS: The study revealed abnormally elevated levels of κ-FLC monomers and dimers in the CSF of 10 MS patients ("κ-type MS"). Increased amounts of λ dimers were found in six MS cases ("λ-type MS"), while high levels of both κ and λ FLC ("mixed type MS") were documented in three MS cases. MRI and clinical assessment showed a more aggressive disease form for the "mixed" and "λ-type" cases. Our method demonstrated higher sensitivity (90.5%) and specificity (91.4%) for discrimination between MS and non-MS patients, as compared to oligoclonality test (81% and 65.7%, respectively). CONCLUSIONS: The proposed method may significantly contribute to diagnosis and prognosis of pediatric MS.

Immunoglobulin-free light chain monomer-dimer patterns help to distinguish malignant from premalignant monoclonal gammopathies: a pilot study.

Multiple myeloma (MM) and AL amyloidosis (AL) are two malignant forms of monoclonal gammopathies. For the purposes of prognosis and treatment, it is important to distinguish these diseases from the premalignant forms of monoclonal gammopathies, such as monoclonal gammopathy of unknown significance (MGUS) and smoldering myeloma (SMM). Routine serum/urine tests for monoclonal protein are insufficient for differential diagnosis. Thus, invasive procedures, such as tissue aspiration or biopsy, are applied. In this study, we aimed at characterization of serum-free light chain (FLC) monomer-dimer patterns to distinguish the malignant from the premalignant forms of monoclonal gammopathies. A quantitative Western blotting was applied to estimate the FLC monomer and dimer levels in AL, MM, MGUS, and SMM patients, and in control subjects (healthy individuals and patients with AA amyloidosis). AL and MM patients displayed an abnormally increased dimerization of monoclonal FLC, accompanied by higher clonality values of FLC dimers, as compared to that of monomers. These abnormalities of FLC patterns were not observed in patients with MGUS, SMM, AA amyloidosis, and healthy individuals. Analysis of FLC patterns helped to differentiate AL and MM from MGUS and SMM, a goal difficult to achieve using routine serum tests. Also, our technique might serve as a complimentary diagnostic tool in the cases with suspected AL amyloidosis, where the diagnosis of MM is excluded, while the results of amyloid typing by routine immunohistochemical techniques are inconclusive.

Personalized Disease Monitoring in Pediatric Onset Multiple Sclerosis Using the Saliva Free Light Chain Test.

Background: Development of new safe methods of monitoring disease activity in the pediatric onset multiple sclerosis (POMS) is a challenging task, especially when trying to refrain from frequent MRI usage. In our recent study, the saliva immunoglobulin free light chains (FLC) were suggested as biomarkers to discriminate between remission and active MS in adults. Objectives: To assess utility of saliva FLC measurements for monitoring disease activity in POMS. Methods: We used semiquantitative Western blot analysis to detect immunoreactive FLC monomers and dimers and to calculate the intensity of their bands. Statistical tests included Firth logistic regression analysis suitable for small sample sizes, and Spearman's non-parametric correlation. Results: In naive POMS patients, the saliva levels of FLC in relapse were significantly higher than those in remission. Significant correlation was found between FLC levels (monomers, dimers or both) and the load of enhanced lesions in MRI scans. FLC levels may be reduced under treatment, especially as result of corticosteroids therapy. Follow-up of individual patients showed the correspondence of changes in the FLC levels to MRI findings. Conclusions: Our results show the potential of the non-invasive saliva FLC test, as a new tool for monitoring the disease activity in POMS.

Saliva immunoglobulin free light chain analysis for monitoring disease activity and response to treatment in multiple sclerosis.

BACKGROUND: Immunoglobulin free light chains (FLC) have recently gained considerable interest as new promising intrathecal biomarkers of multiple sclerosis (MS). However, lumbar puncture is invasive and not practical for monitoring disease course. This study aimed to assess the utility of saliva FLC as a biomarker of disease activity and response to treatment in MS METHODS: Western blotting was used to study saliva FLC monomers and dimers. The intensity of immunoreactive FLC bands was quantified by electrophoresis analysis, and the obtained values were used as FLC indices to account for kappa and lambda FLC monomer and dimer levels. Firth's logistic regression analysis suitable to study small cohorts was applied to compare FLC levels between M.S. patients in relapse, MS patients in remission, and healthy controls. Association between FLC levels and clinical and radiological parameters was analyzed. RESULTS: 55 MS patients and 40 healthy controls were evaluated. Saliva FLC levels were significantly higher in relapse compared to remission. Logistic regression analysis employing a combination of FLC indices confirmed the significant difference between these two groups. The FLC levels were significantly reduced by treatment with corticosteroids. During remission, patients treated with disease-modifying therapies had lower levels of FLC compared to untreated patients. The increased FLC levels were associated with the presence of gadolinium-enhancing lesions, but not with MRI T2 lesion load and EDSS scores. During individual patient follow-up, the changes of the saliva FLC levels were in concordance with the disease activity status. CONCLUSIONS: Saliva FLC levels may be a useful biomarker for discriminating between stable remission and active disease. The developed test may serve as a new, non-invasive, and inexpensive tool for monitoring disease activity and response to treatment in MS.

Free light chain monomer-dimer patterns in the diagnosis of multiple sclerosis.

In our search of new biomarkers for multiple sclerosis (MS), we aimed to characterize the immunoglobulin (Ig) free light chains (FLC) in patients' cerebrospinal fluid (CSF) and serum, and to evaluate the diagnostic utility of FLC monomer-dimer patterns for MS. FLC were analyzed by Western blotting and mass spectroscopy. CSF and serum samples were examined for the presence of oligoclonal Ig bands by a conventional laboratory test for MS. Three distinct pathological FLC monomer-dimer patterns, typical of MS but not of other neurological diseases, were revealed. In 31 out 56 MS patients the highly increased CSF levels of κ monomers and dimers were demonstrated. In 18 MS patients, the increased κ-FLC levels were accompanied by highly elevated λ dimers. Five MS cases showed no significant elevation in κ-FLC, but they displayed abnormally high λ dimer levels. The intensity of the immunoreactive FLC bands was measured to account for κ and λ monomer and dimer levels and their ratios in the CSF and serum. Combined usage of different FLC parameters allowed the determination of the appropriate FLC threshold values to diagnose MS. The developed method showed higher sensitivity and specificity (96% and 90%, respectively), as compared to those of the conventional OCB test (82% and 70%, respectively). Our study highlights the role of the differential analysis of monomeric and dimeric κ- and λ-FLC for the precise diagnosis of MS.

Free light chain monomers in the diagnosis of multiple sclerosis.

A new procedure of free light chain (FLC) analysis was developed to assist the diagnosis of multiple sclerosis (MS). In this procedure, Western blotting technique was used to analyze monomeric and dimeric FLCs in the cerebrospinal fluid (CSF) and serum of patients with MS and other neurological diseases. The intensity of immunoreactive FLC bands was quantified by a specially developed software. Analysis of the obtained monomer/dimer patterns of κ and λ type FLCs allowed the determination of the diagnostically useful FLC parameters. The combined use of three FLC indices accounting for monomeric FLC-κ level and κ/λ ratio values in the CSF and serum was found to be of promising diagnostic importance for differentiation of MS from other non-MS neurological diseases.