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Isolated hypogammaglobulinemia (IH) is an electrophoretic pattern that can be encountered on serum protein electrophoresis (SPEP) and is defined as a decreased but morphologically normal γ-globulin fraction with normal α- and β-globulin fractions. SPEP is mainly used to detect monoclonal proteins which are usually observed as additional peaks in the electropherogram. However, they may also be more discretely present in a significant proportion of patients presenting with IH. Therefore, we aimed to evaluate i) via both retrospective and prospective analysis to what extent paraproteins as identified by immunofixation are present in patients demonstrating IH on SPEP and ii) whether other parameters may predict their presence in IH-patients. For this purpose, we first reviewed historic SPEP- and immunofixation results in our tertiary hospital and determined paraprotein prevalence in this retrospective cohort. This analysis showed immunofixation was requested in only 519/3938 (13.2%) historic IH-results with 52/519 (10%) patients demonstrating paraproteins. Next, various laboratory parameters were compared between paraprotein-positive and -negative patients and subjected to logistic regression models but regrettably, no parameter could be retained as promising predictor of paraproteins. Lastly, to confirm paraprotein prevalence seen in the historical query, we conducted a six-month prospective analysis during which immunofixation was requested more frequently in IH-cases during routine diagnostics and which showed paraproteins to be present in 20/83 (24.1%) of IH-patients. Hence, as up to 24% of patients with IH may harbour paraproteins, one should consider performing follow-up analyses (e.g. immunofixation, urine electrophoresis and/or free light chain analysis) for all IH-cases identified via SPEP.

Antibodies to dsDNA are an important laboratory parameter for diagnosis, monitoring and classification of systemic lupus erythematosus (SLE). In clinical laboratories, several techniques are used to detect and quantify anti-dsDNA antibodies. Each technique has its advantages and disadvantages regarding sensitivity, specificity, avidity and assay procedure. Assays differ with respect to the antigen source (native versus synthetic versus molecular biological) used and the way the antigen is presented (e.g. in solution, covalently linked to a solid phase,…). Consequently, correlation between assays can be poor and standardization of anti-dsDNA antibody tests is challenging. We here provide an overview of the currently available anti-dsDNA tests frequently used in clinical laboratories [Crithidia luciliae immunofluorescence test (CLIFT), Enzyme linked immune sorbent assay (ELISA), fluoroenzyme immunoassay (FEIA), chemiluminisence immunoassay (CIA), multiplexed bead-based assays and Farr-RIA] and their performance characteristics. From this literature study, we concluded that performance characteristics differ between assays. Often, a combination of techniques is necessary for the best result interpretation., (Copyright © 2022 Elsevier B.V. All rights reserved.)