Electrophoresis and densitometry of serum and urine in the investigation and significance of monoclonal immunoglobulins

Rapid and regenerable surface plasmon resonance determinations of biomarker concentration and biomolecular interaction based on tris-nitrilotriacetic acid chips

The tris-nitrilotriacetic acid (tris-NTA) chip has been used for surface plasmon resonance (SPR) kinetic studies involving histidine (His)-tagged proteins. However, its full potential, especially for analyte quantification in complex biological media, has not been realized due to a lack of systematic studies on the factors governing ligand immobilization, surface regeneration, and data analysis. We demonstrate that the tris-NTA chip not only retains His-tagged proteins more strongly than its mono-NTA counterpart, but also orients them more uniformly than protein molecules coupled to carboxymethylated dextran films. We accurately and rapidly quantified immunoglobulin (IgG) molecules in sera by using the initial association phase of their conjugation with His-tagged protein G densely immobilized onto the tris-NTA chip, and established criteria for selecting the optimal time for constructing the calibration curve. The method is highly reproducible (less than 2% RSD) and three orders of magnitude more sensitive than immunoturbidimetry. In addition, we found that the amount of His-protein immobilized is highly dependent on the protein isoelectric point (pI). Reliable kinetic data in a multi-channel SPR instrument can also be rapidly obtained by using a low density of immobilized His-tagged protein. The experimental parameters and procedures outlined in this study help expand the range of SPR applications involving His-tagged proteins.

A Study on Free Light Chain Assay and Serum Immunofixation Electrophoresis for the Diagnosis of Monoclonal Gammopathies

Demonstration of monoclonal immunoglobulin molecule in serum forms the mainstay in the diagnosis of monoclonal gammopathies. The major tests that help in this regard are serum protein electrophoresis (SPEP), serum immunofixation electrophoresis (sIFE) and serum free light chain assay (sFLC). Our objectives were to study the accuracy of sFLC and sIFE in the diagnosis of monoclonal gammopathies and also to study the role of combination of SPEP + sIFE + sFLC in the diagnosis of the same. 46 patients who attended the hemato-oncology clinic with signs and symptoms suggestive of monoclonal gammopathy were enrolled in this study. SPEP, sIFE, sFLC and pre-treatment serum beta-2 microglobulin levels were analysed among the study population. Both SPEP and sIFE were performed in the Interlab Genios fully automated machine. Serum beta-2 microglobulin and sFLC were estimated by immunoturbidimetry in Beckman Coulter AU 2700 analyzer. The accuracy of sIFE came to be 80% with respect to sFLC assay. Sensitivity, specificity, positive and negative predictive value of sIFE with respect to sFLC were 81.3, 78.6, 89.7 and 64.7% respectively. It was observed that a combination panel of SPEP + sIFE + sFLC could detect all the cases of myeloma included in this study. Further testing in large samples is required for generalising the findings of this study. The pre-treatment beta-2 microglobulin levels were significantly higher in the group which was positive for myeloma. A combination panel of SPEP + sIFE + sFLC prove to be more useful than individual tests for the detection of myeloma.

Serum proteins profile as an indicator of malignancy: multivariate logistic regression and ROC analyses

The electrophoretic pattern of serum proteins of 85 patients carrying different types of neoplasia and 85 matched healthy adults were comparatively studied by agarose gel electrophoresis, to find out if there is a specific protein pattern common to different types of cancer. Each protein fraction was analyzed quantitatively by densitometry. Multivariate logistic regression and receiver operating characteristic (ROC) analyses were performed using SPSS software. When total protein and albumin were measured by colorimetric methods, cancer patients, compared to controls, had a decreased concentration of total protein (66.0+/-11.5 g/L vs. 76.4+/-6.8 g/L, p< or =0.0001) and of albumin (39.0+/-8.1 g/L vs. 46.0+/-4.3 g/L, p< or =0.0001). The electrophoretic data of serum proteins showed that the ratio of albumin to globulin (0.92+/-0.30 vs. 1.21+/-0.16, p< or =0.0001), percent of the fractions albumin (46.7+/-8.5% vs. 54.4+/-3.5%, p< or =0.0001) and beta-globulin (11.6+/-4.4% vs. 13.0+/-1.9%, p< or =0.001) were decreased and alpha(1)- (5.3+/-2.5% vs. 2.9+/-0.8%, p< or =0.0001), alpha(2)- (13.5+/-4.8% vs. 11.3+/-2.1%, p< or =0.0001) and gamma-globulins (23.0+/-7.7% vs. 18.3+/-3.1%, p< or =0.0001) were significantly increased in cancer patients relative to controls. Cancer patients also had higher counts of leukocytes (7.98+/-3.11, x10(9) cells/L vs. 6.33+/-1.68 x10(9) cells/L, p< or =0.0001) and erythrocyte sedimentation rate (35.9+/-23.5 mm/h vs. 14.1+/-9.5 mm/h,p< / =0.0001). On the basis of univariate analysis, a protein profile out of the normal ranges was more prevalent in cancer patients than in controls. Analysis of the data using multiple logistic regression indicated that the prevalence of cancer was strongly associated with the serum proteins' profile, and alpha(1)-globulin, erythrocyte sedimentation rate, total protein and the ratio of albumin to globulin were the best parameters to discriminate between malignant and healthy states. The area under the ROC curves were the same for most components of the serum proteins' profile at about 0.75+/-0.09, p< or =0.001. We conclude that the profile of serum proteins indicates high diagnostic values for discriminating between cancer patients and healthy individuals and may be useful as an adjunct diagnosis for detection of malignancy.

Monitoring of monoclonal gammopathies: rational use of densitometry and rate nephelometry

The follow-up of patients with monoclonal gammopathies at our institution includes serial serum protein electrophoresis (SPE) with densitometry and IgG, IgA, and IgM quantitative immunoglobulin (QIG) determinations by rate nephelometry. This retrospective audit compares monoclonal protein concentration as estimated by SPE versus QIG in 456 serial serum specimens from 105 patients to determine whether any of the tests provide redundant information. A comparison of the methods demonstrated good correlation between SPE (x-axis) and QIG (y-axis) quantitation for each immunoglobulin class: IgG had a slope of 1.45 and an intercept of 1.60 (Sy/x = 7.46, r = 0.96, n = 250); IgA had a slope of 1.30 and an intercept of -1.37 (Sy/x = 6.85, r = 0.96, n = 78); and IgM had a slope of 1.95 and an intercept of 2.06 (Sy/x = 5.16, r = 0.98, n = 128). The data for individual patients showed similar good correlations. Exceptions included IgA peaks "buried" in the beta region of the SPE (resulting in invalid SPE estimates of monoclonal protein concentration), and IgG peaks of less than 10 g/L (when background polyclonal IgG immunoglobulin skews the QIG estimate of monoclonal protein concentration). An algorithm is proposed whereby monoclonal protein concentration is measured by the specific QIG (i.e., IgG, IgA, or IgM) determination for the routine monitoring of patients, except for those with IgG peaks of less than 10 g/L that are followed by SPE.