IgMκ-IgMλ pair quantitation in the clinical laboratory practice

Cryoglobulins: Identification, classification, and novel biomarkers of mysterious proteins

Cryoglobulins consist of serum immunoglobulins that precipitate below 37°C and resolubilize upon warming. The clinical triad of cryoglobulinemia usually includes purpura, weakness, and arthralgia. Cryoglobulinemic syndrome, clinically defined as a systemic vasculitis, is associated with chronic infection with hepatitis C virus (HCV) and autoimmune disorders and can evolve into B-cell malignancies. While the current literature about HCV-associated cryoglobulinemia is not very limited, little is known about the immunologic and serologic profiles of affected patients. Therefore, comprehension of the pathogenetic mechanisms underlying cryoprecipitation could be very helpful. Due to the persistence of viral antigenic stimulation, biomarkers to use after the worsening progression of HCV infection to lymphoproliferative and/or autoimmune diseases are widely needed. Laboratory methods used to detect and characterize low concentrations of cryoprecipitates and immunotyping patterns could improve patient management. The most critical factor affecting cryoglobulin testing is that the pre-analytical phase is not fully completed at 37°C.

Biomarkers of minimal residual disease in rituximab-treated patients with mixed cryoglobulinemia

Hepatitis C virus (HCV) represents the major risk factor for mixed cryoglobulinemia (MC), a small-vessel vasculitis that may evolve into an overt B-cell non-Hodgkin's lymphoma. Here, we aimed to identify a biomarker signature for the early diagnosis of minimal residual disease (MRD). We assessed free light chains (FLCs), IgM k,and IgM λ heavy/light chain (HLC) pairs, and vascular endothelial growth factor (VEGF) in sera from 34 patients with MC vasculitis (32 HCV- and 2 HBV-related), treated with low-dose rituximab (RTX). FLCs and IgM HLCs were measured by turbidimetric assay; VEGF by an enzyme-linked immunosorbent assay. After RTX, the positive (complete + partial) clinical and laboratory responses were of 85.29% and 50%, respectively; in contrast, the mean levels of FLCs, IgM HLCs, and VEGF were substantially unaffected in most patients and still above the normal range. In those achieving a reduction of FLCs and IgM k and λ chains values within the range of normality, we found that post-treatment free λ chains and IgM k values correlated with clinical and laboratory response. Our results suggest that high levels of FLCs, IgM HLCs, and VEGF could represent the signature of "dormant" B cell clones' activity that could be very useful to identify MRD indicative of possible relapse or worsening outcome.

Serum markers in the differential diagnosis of Waldenstrom macroglobulinemia and other IgM monoclonal gammopathies

BACKGROUND

IgM monoclonal gammopathy can be present in a broad spectrum of diseases. We evaluated the value of serum markers in the differential diagnosis of Waldenstrom macroglobulinemia (WM) and other types of IgM monoclonal gammopathies.

METHODS

We included patients who were first admitted to hospital and identified as having IgM monoclonal gammopathy by serum immunofixation electrophoresis (sIFE). We evaluated basic clinical features, sIFE, diagnosis, and serum markers. Furthermore, we applied the receiver operating characteristic (ROC) curve to analyze the differential diagnosis value of serum markers for WM. Finally, we used logistic regression and ROC curve to analyze the differential diagnosis value of multimarker combinations to identify WM.

RESULTS

IgM monoclonal gammopathy was most frequently found in patients with Waldenstrom macroglobulinemia, followed by monoclonal gammopathy of undetermined significance (MGUS), B-cell non-Hodgkin Lymphoma (B-NHL), and multiple myeloma (MM). Serum markers showed significant differences among the four diseases. The diagnostic markers LDH, IgM, IgG, IgA, and serum light chain К had higher diagnostic efficiency. Among these markers, serum IgM provided the highest diagnostic efficiency. Additionally, the combined use of all five serum markers provided the most effective diagnosis.

CONCLUSIONS

The five serum markers, LDH, IgM, IgG, IgA, and К, each yielded a specific efficacy in differential diagnosis of WM. The single marker with the highest diagnostic efficiency was the serum IgM level. However, a combination of multiple serum markers was better than the use of a single marker in diagnosing WM. The combined use of all five serum markers provided the most effective diagnosis, with an AUC of .952 and sensitivity and specificity of 87.8% and 86.9%, respectively.