Evaluation of high resolution gel ß(2)-transferrin for detection of cerebrospinal fluid leak.

BACKGROUND: Cerebrospinal fluid (CSF) leaks are potentially life-threatening conditions that can be diagnosed by detection of ß(2)-transferrin using protein electrophoresis. Another less commonly available test is ß-trace protein quantitation using immunoassay. The objectives of this study were to evaluate a new immunofixation-based ß(2)-transferrin test for detection of CSF leaks and to compare it to an existing agarose gel electrophoresis test and ß-trace protein immunoassay. METHODS: For method comparison, 63 consecutive samples from physician-ordered ß(2)-transferrin tests were analyzed using two different electrophoresis methods, agarose gel fractionation followed by acid-violet staining, and high resolution agarose gel electrophoresis followed by ß(2)-transferrin immunofixation. A subset of samples (16/63) were analyzed for ß-trace protein. Results were compared against patient chart data for the presence of a CSF leak. Additional studies were performed to assess the stability, detection limit, and analytical specificity of the ß(2)-transferrin immunofixation test. RESULTS: The ß(2)-transferrin immunofixation test had a sensitivity of 100 % (40/40) and specificity of 71 % (12/17) for detection of CSF leaks. By comparison, the agarose gel test had a sensitivity of 87 % (35/40) and specificity of 94 % (16/17). ß-trace protein had a sensitivity of 100 % (10/10) and specificity of 86 % (5/6). Serum and saliva could be differentiated from CSF by the ß(2)-transferrin immunofixation test based on their migration patterns. However, whole blood samples appeared positive for ß(2)-transferrin at a threshold of ~ 4 g/L hemoglobin. At a cut-off of 3 mg/L, ß-trace protein was increased in 10/10 cases with documented CSF leak and in 1/6 patients without CSF leak. CONCLUSIONS: Both the new immunofixation test for ß(2)-transferrin and the ß-trace protein were effective at detecting CSF leaks. Users of the ß(2)-transferrin immunofixation test should be cautioned against interpreting samples with blood contamination.

Performance evaluation of the Helena V8 capillary electrophoresis system.

OBJECTIVES: To compare the performance characteristics of the Helena V8® and Sebia CAPILLARYS2® automated capillary electrophoresis systems to agarose gel serum protein electrophoresis (SPE) and immunofixation electrophoresis (IFE) using the Helena SPIFE3000®. DESIGN AND METHODS: Serum protein electrophoresis and immunosubtraction was performed on 100 consecutive patient samples comparing two capillary-electrophoresis platforms with agarose-gel SPE and IFE; IFE was used as the gold standard. Chart review was performed on patients where results were discordant between methods. Analytical precision was determined using Sebia's normal and abnormal controls. RESULTS: The sensitivities of the CAPILLARYS2, V8, and SPIFE3000 agarose gel for identification of monoclonal gammopathies were respectively 97.4 (95%CI 91.1-100), 92.3 (95%CI 82.2-100), and 89.9 (95%CI 79.1-97.6). The specificities of the CAPILLARYS2, V8, and SPIFE3000 agarose gel were respectively 57.6 (95%CI 45.0-70.2), 72.2 (95%CI 61.0-83.3), and 75.4 (95%CI 60-82.8). These analytical performance characteristics were statistically equivalent between systems (P>0.05). The analytical precision of the capillary-based methods was also statistically equivalent. Chart review of available data from discordant samples revealed that 7/10 patients had a history of multiple myeloma or known monoclonal gammopathy and were being treated or monitored. All discordant samples had low concentration monoclonal proteins (<0.3g/dL). Both capillary-based methods performed poorly (collectively <50% accuracy) at detecting low concentration non-IgG antibodies (IgA, IgM, and light chain monoclonal gammopathies) compared to IFE. CONCLUSIONS: The Helena V8 and Sebia CAPILLARYS2 were analytically equivalent to the SIFE3000 for identification of IgG monoclonal gammopathies >0.3g/dL. Interpreters using the automated immunotyping/immunosubstraction systems performed poorly at detecting low concentration and non-IgG monoclonal gammopathies.

Performance comparison of capillary and agarose gel electrophoresis for the identification and characterization of monoclonal immunoglobulins.

The objective of this study was to compare gel- and capillary-based serum protein electrophoresis methods to identify and characterize monoclonal immunoglobulins (M proteins). Five reviewers interpreted 149 consecutively ordered serum specimens following agarose gel electrophoresis (AGE), capillary electrophoresis (CE), immunofixation electrophoresis (IFE), and subtraction immunotyping (IT). As a screening test for detecting M proteins, AGE and CE displayed similar sensitivity (91% and 92%, respectively). CE was less specific (74%) than AGE (81%). An analysis of interinterpreter agreement revealed that interpretations were more consistent using gel-based methods than capillary-based methods, with 80% of the gel interpretations being in complete (5/5) agreement compared with 67% of the capillary interpretations. After implementing the capillary-based methods, the number of tests per reportable result increased (from 1.58 to 1.73). CE is an analytically suitable alternative to AGE, but laboratories implementing it will need to continue IFE testing to characterize all M proteins detected by CE.