Background Electrophoretic methods to detect, characterize and quantify M-proteins play an important role in the management of patients with monoclonal gammopathies (MGs). Significant uncertainty in the quantification and limit of detection (LOD) is documented when M-proteins are <10 g/L. Using spiked sera, we aimed to assess the variability in intact M-protein quantification and LOD across 16 laboratories. Methods Sera with normal, hypo- or hyper-gammaglobulinemia were spiked with daratumumab or elotuzumab, with concentrations from 0.125 to 10 g/L (n = 62) along with a beta-migrating sample (n = 9). Laboratories blindly analyzed samples according to their serum protein electrophoresis (SPEP)/isotyping standard operating procedures. LOD and intra-laboratory percent coefficient of variation (%CV) were calculated and further specified with regard to the method (gel/capillary electrophoresis [CZE]), gating strategy (perpendicular drop [PD]/tangent skimming [TS]), isotyping (immunofixation/immunosubtraction [ISUB]) and manufacturer (Helena/Sebia). Results All M-proteins ≥1 g/L were detected by SPEP. With isotyping the LOD was moderately more sensitive than with SPEP. The intensity of polyclonal background had the biggest negative impact on LOD. Independent of the method used, the intra-laboratory imprecision of M-protein quantification was small (mean CV = 5.0%). Low M-protein concentration and high polyclonal background had the strongest negative impact on intra-laboratory precision. All laboratories were able to follow trend of M-protein concentrations down to 1 g/L. Conclusions In this study, we describe a large variation in the reported LOD for both SPEP and isotyping; overall LOD is most affected by the polyclonal immunoglobulin background. Satisfactory intra-laboratory precision was demonstrated. This indicates that the quantification of small M-proteins to monitor patients over time is appropriate, when subsequent testing is performed within the same laboratory.

Background Serum protein electrophoresis (SPEP) is used to quantify the serum monoclonal component or M-protein, for diagnosis and monitoring of monoclonal gammopathies. Significant imprecision and inaccuracy pose challenges in reporting small M-proteins. Using therapeutic monoclonal antibody-spiked sera and a pooled beta-migrating M-protein, we aimed to assess SPEP limitations and variability across 16 laboratories in three continents. Methods Sera with normal, hypo- or hypergammaglobulinemia were spiked with daratumumab, Dara (cathodal migrating), or elotuzumab, Elo (central-gamma migrating), with concentrations from 0.125 to 10 g/L (n = 62) along with a beta-migrating sample (n = 9). Provided with total protein (reverse biuret, Siemens), laboratories blindly analyzed samples according to their SPEP and immunofixation (IFE) or immunosubtraction (ISUB) standard operating procedures. Sixteen laboratories reported the perpendicular drop (PD) method of gating the M-protein, while 10 used tangent skimming (TS). A mean percent recovery range of 80%-120% was set as acceptable. The inter-laboratory %CV was calculated. Results Gamma globulin background, migration pattern and concentration all affect the precision and accuracy of quantifying M-proteins by SPEP. As the background increases, imprecision increases and accuracy decreases leading to overestimation of M-protein quantitation especially evident in hypergamma samples, and more prominent with PD. Cathodal migrating M-proteins were associated with less imprecision and higher accuracy compared to central-gamma migrating M-proteins, which is attributed to the increased gamma background contribution in M-proteins migrating in the middle of the gamma fraction. There is greater imprecision and loss of accuracy at lower M-protein concentrations. Conclusions This study suggests that quantifying exceedingly low concentrations of M-proteins, although possible, may not yield adequate accuracy and precision between laboratories.

Proteome analysis represents a promising approach for plant tissue culture since it is now possible to identify and quantify proteins on a large scale. Biomarker discovery and the study of the molecular events associated with in vitro plant morphogenesis are considered potential targets for application of proteomics technologies. This chapter describes a protocol for application in in vitro plant material using two proteomics approaches: 2-DE coupled to mass spectrometry and liquid chromatography-linked tandem mass spectrometry.

BACKGROUND: Patients with Sjögren\'s syndrome (SS) have a considerable higher risk of lymphoma development.
OBJECTIVE: To determine the incidence of lymphoma and the value of biomarkers to predict lymphoma development in patients with SS.
METHODS: Clinical files of all patients with a presumed diagnosis of SS between 1991 and 2016 were retrospectively reviewed for the development of lymphoma. Biochemical data were plotted as a function of the relative time before and after the lymphoma diagnosis (for patients who developed lymphoma) or before the last available blood test (for patients who did not develop lymphoma). Correlations between several biochemical parameters and development of lymphoma were analyzed by logistic regression. In order to evaluate the evolution of cryoglobulins, a random effect model with random intercepts was used.
RESULTS: Sixteen patients developed a lymphoma (prevalence 8.9%; median follow-up 6 years). Cryoglobulins were significantly higher in these patients (n = 16), when compared to the rest of patients (n = 164) without lymphoma (121 ± 250 versus 8 ± 24.9 mg/L for IgG; 231 ± 422 versus 13 ± 30 mg/L for IgM; 10 ± 20 versus 1 ± 4 mg/L for IgA in the cryoprecipitate). Cryoglobulin-levels were significantly more increasing (p-values for IgG = 0.0007; for IgM = 0.0123; and for IgA in the cryoprecipitate <0.0001) in the time period before the lymphoma diagnosis (patients with lymphoma) compared to the time period before the last available blood test (patients without lymphoma). Also low (i.e. under the detection limit) C3 (OR 13.9) or C4 (OR 7.1) levels, a progressively decreasing total complement activity (OR 6.6), progressively decreasing gammaglobulins (OR 13.4), a persistent detection of monoclonal bands (OR 14.6) on protein electrophoresis, a persistent low or decreasing serum IgG (OR 18), and decreasing IgM-serum levels (OR 17.7) were significantly associated with lymphoma.
CONCLUSIONS: Periodically follow-up of laboratory markers, such as cryogloblins, over time proved to be an accurate way to predict lymphoma.