Clinical applications of immunofixation: a more sensitive technique for the detection of Bence Jones protein

Bead-Based Immunocomplex Entrapment Assays for Rapid, Sensitive, and Multiplexed Detection of Disease Biomarkers with Minimal User Intervention

Current interest in at-home diagnostic devices derives from their potential to disrupt expensive and time-consuming hospital-based diagnostic practices. Conventional immunoassays are often touted for use in at-home diagnostic devices, although in practice they are slow, labor-intensive and require expensive equipment. Here, we introduce bead-based sensors as alternative biomarker detection platforms for at-home diagnostic devices. The immunocomplex entrapment assay (ICEA), and the related enzyme-linked ICEA (ELICEA) offer enhancements over conventional immunoassays in terms of their speed, and minimal requirements for user intervention and instrumentation. In particular, we designed bead-based sensors to entrap large molecular weight complexes between target molecules and signal-generating immunoconjugates while allowing any unbound conjugates to escape from the bead. Confocal fluorescence microscopy was used to demonstrate the sensitivity, robustness, and reproducibility of the ICEA and ELICEA platforms. For example, we showed the intensity of signals generated by entrapped immunoconjugate complexes correlate linearly with the concentration of target molecule in the sample. We employed ICEA, and ELICEA platforms to detect human forms of immunoglobulins, albumin, and κ light chain (KLC). For example, we used ICEA to detect KLC at 5 μg·mL^-1 in urine, which would allow for earlier diagnosis of Bence-Jones disease compared to conventional assays. In addition, we showed bead-entrapped phosphatases (AP) in immunocomplexes generate insoluble, blue-colored dyes from AP-substrates that accumulate in beads and allow for visual and cellphone camera-based detection of IgG to 10 ng·mL^-1 within 20 min. Finally, we described ICEA and ELICEA platforms to analyze multiple target proteins within individual beads.

The Paraprotein - an Enduring Biomarker

The 'paraprotein', also known as M-protein, monoclonal protein and monoclonal component, has stood the test of time as the key biomarker in monoclonal gammopathies. It continues to reinvent itself as new electrophoretic and immunoassay methods are developed that are analytically more sensitive. Use of the serum free light chain immunoassay in particular has led to new clinical discoveries and improvements in the diagnosis and monitoring of patients with plasma cell dyscrasia and other monoclonal gammopathies. In addition, minimal residual disease can be detected using mass spectrometry and flow cytometry methods.

The evaluation of distal symmetric polyneuropathy: a physician survey of clinical practice

OBJECTIVE

To define current clinical practice for evaluating distal symmetric polyneuropathy.

DESIGN

Using a modified Dillman method, we sent surveys to 600 internists, 600 neurologists, and 45 neuromuscular specialists selected from the American Medical Association Physician Masterfile. Survey questions pertained to which tests providers would order in the following 3 scenarios: (1) the initial evaluation of distal symmetric polyneuropathy, (2) the use of additional tests if the initial evaluation was unrevealing, and (3) patients with diabetes. The t test was used to compare the number of tests ordered by physician type, and the χ(2) test was used to compare proportions of tests ordered.

SETTING

National survey of physicians.

PARTICIPANTS

Internists, neurologists, and neuromuscular specialists.

RESULTS

The response rate was 35%. Overall, many tests were ordered for the full evaluation of distal symmetric polyneuropathy (mean [SD], 16.5 [7.2] tests), and there was substantial variation within and between provider types. Internists ordered fewer tests (mean [SD], 14.5 [6.1] tests) than did neurologists (mean [SD], 17.5 [7.9] tests) (P < .001). Regarding the glucose tolerance test, substantial differences were found between physician types, with neurologists and neuromuscular specialists ordering this test more frequently (28.6% and 72.3%, respectively) and internists ordering it less frequently (4.1%). A brain and/or spine magnetic resonance imaging scan was ordered by 19.8% of internists and 12.9% of neurologists.

CONCLUSIONS

From the supporting evidence, current practice intent on evaluating distal symmetric polyneuropathy is highly variable and differs widely. For this disorder of the peripheral nerves, a high-yield test such as the glucose tolerance test is rarely used, whereas magnetic resonance imaging is likely overused. Research that defines the optimal evaluation of distal symmetric polyneuropathy has the potential to result in more efficient care.

High-sensitivity electrophoretic method for the detection of Bence Jones protein and for the study of proteinuria in unconcentrated urines

The study of proteinuria, and especially the search for Bence Jones proteins (BJP), has almost always required urine concentration. We evaluated a high-sensitivity electrophoretic method using unconcentrated urine based on colloidal gold staining. The sensitivity for the detection of BJP is further enhanced by immunofixation. Sensitivity to BJP is better than 1 mg/L and, apart from the alpha-1 microglobulin, all the proteins relevant to the classification of proteinuria can be visualized with a sensitivity of approximatively 3 mg/L.

Monoclonal free light chains in urine and their significance in clinical diagnostics: are they really tumor markers?

Bence Jones proteins (monoclonal free light chains of immunoglobulins) are the earliest known biological markers of malignant cell dyscrasia; Bence Jones proteinuria is also present in many types of B cell-related neoplasms. Sometimes, it may also occur in Hodgkin's disease. In some cases, benign monoclonal gammapathy was found to be associated nontumorous diseases as well. The type of monoclonal light chain, the degree of polymerization, and the isoelectric point of the molecule may affect the course of the disease. Urine samples from 637 patients with true or suspected lymphoproliferative diseases were investigated over a 2-yr period by different immunochemical methods. Bence Jones proteinuria was identified in 71 cases by isoelectric focusing combined with immunofixation, while the pathological protein was detected only in 63 cases by conventional methods. Bence Jones proteins can be detected by this new method at a level below the sensitivity of conventional procedures. Bence Jones proteins in the urine may signal a malignant tumor or malignant transformation of an earlier disease. The early detection of monoclonal immunoglobulin light chains in the urine may be important in clinical diagnosis, therapy, and follow-up.

Effects of sodium dodecylsulphate, dye concentration and paraprotein on coomassie blue dye-binding assays for protein in urine

Various Coomassie Blue reagents, containing either increased dye concentration or added sodium dodecylsulphate, were compared with a biuret method for the assay of total protein in urine. When immunoglobulin free light chain protein or immunoglobulin paraprotein were present, results from the Coomassie Blue methods were up to 50% lower than with the biuret method; increased dye concentration did not improve comparability substantially, but the addition of sodium dodecylsulphate reduced the bias to about 20%. When neither free light chain protein nor immunoglobulin paraprotein was present, results from the Coomassie Blue methods were only about 30% lower. The addition of sodium dodecylsulphate reduced this bias to 10%. Correlations between the biuret and the Coomassie Blue method were best when the Coomassie Blue reagent contained 40 mg/L sodium dodecylsulphate (r better than 0.98 in all groups; p less than 0.001).

Plasma cell dyscrasias: current status

This is a review of the current status of the monoclonal gammopathies (plasma cell dyscrasias). We begin with the recognition of a monoclonal protein in serum and urine. We briefly discuss the differential diagnosis of the monoclonal gammopathies. Clinical and laboratory findings as well as the management of multiple myeloma are addressed. Future approaches for the treatment of myeloma are provided. The variant forms of multiple myeloma, including smoldering myeloma, plasma cell leukemia, nonsecretory myeloma, IgD myeloma, osteosclerotic myeloma, solitary plasmacytoma of bone, and extramedullary plasmacytoma, are briefly reviewed. Diagnosis and treatment of Waldenström's macroglobulinemia are presented. The recognition and differential diagnosis of the heavy-chain diseases (gamma, alpha, and mu) are included. Monoclonal gammopathy of undetermined significance ("benign" monoclonal gammopathy) is presented in detail. Amyloidosis is not included in this review.

Instantaneous roll-blot from cellulose acetate after electrophoresis. A versatile tool for monoclonal antibody characterization

An instantaneous blotting method from cellulose acetate to nitrocellulose was developed using a high pressure roll apparatus. This method was applied to the early characterization of monoclonal antibody specificity and to monoclonal immunoglobulin typing in mouse hybridoma supernatants, human sera or unconcentrated urines. Immunoglobulins were then revealed using, successively, anti-isotype specific monoclonal or polyclonal antibodies, avidin-biotinylated peroxidase complexes and cobalt-enhanced diaminobenzidine substrate.

Bence Jones protein detection: a rapid immunoblotting technique for routine use on unconcentrated urine

A new immunoblotting method is described for the detection of Bence Jones proteinuria by the routine laboratory. Unconcentrated urine specimens are subjected to electrophoresis on agarose gels. Separated proteins are transferred to a nitrocellulose membrane and the immunoglobulins located and identified by horseradish-peroxidase double-antibody staining. The new method has been compared with that used routinely, and an improved rate of detection of both Bence Jones protein and intact urinary monoclonal immunoglobulin has been obtained. Among urine specimens received for routine testing for Bence Jones protein from 83 patients, 64 monoclonal components were found by the new technique compared with 45 by the method used routinely. Other advantages of the new procedure include: no need to concentrate urine specimens before electrophoresis; unlike immunofixation, the proteins may be detected successfully over a wide concentration range without using several specimen or antibody dilutions; and interpretation is easier.

Detection of Bence-Jones protein by isoelectric focussing of unconcentrated urine followed by nitrocellulose blotting and immunoperoxidase staining

Urine specimens from 164 patients sent to the laboratory for testing for Bence-Jones proteinuria were investigated using a new procedure. The protein in the untreated urine was subjected to isoelectric focussing in an agarose gel, transferred to a nitrocellulose membrane by blotting, and then stained by an immunoperoxidase technique for either immunoglobulin kappa or lambda chains. This technique was compared with a routine procedure for the detection of immunoglobulin light chains involving concentration by ultrafiltration, electrophoresis and then immunofixation. The new technique achieved a much increased rate of detection of Bence-Jones proteinuria. Among 51 patients known to have myeloma or macroglobulinaemia, Bence-Jones proteinuria was detected in 35 cases with the new procedure and in only 27 by the conventional method. In 28 patients with paraproteinaemia without other evidence of myeloma, macroglobulinaemia, leukaemia or lymphoma, 12 instances of Bence-Jones proteinuria were discovered with the new procedure, 10 of which were missed by the conventional method. The improved efficiency of detection is attributed to the high resolution of isoelectric focussing and the avoidance of protein loss from adsorption on to ultrafiltration membranes.