Evaluation of high resolution gel β2-transferrin for detection of cerebrospinal fluid leak

Abstract

Abstract Background: Cerebrospinal fluid (CSF) leaks are potentially life-threatening conditions that can be diagnosed by detection of β2-transferrin using protein electrophoresis. Another less commonly available test is β-trace protein quantitation using immunoassay. The objectives of this study were to evaluate a new immunofixation-based β2-transferrin test for detection of CSF leaks and to compare it to an existing agarose gel electrophoresis test and β-trace protein immunoassay. Methods: For method comparison, 63 consecutive samples from physician-ordered β2-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 β2-transferrin immunofixation. A subset of samples (16/63) were analyzed for β-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 β2-transferrin immunofixation test. Results: The β2-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). β-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 β2-transferrin immunofixation test based on their migration patterns. However, whole blood samples appeared positive for β2-transferrin at a threshold of ∼4 g/L hemoglobin. At a cut-off of 3 mg/L, β-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 β2-transferrin and the β-trace protein were effective at detecting CSF leaks. Users of the β2-transferrin immunofixation test should be cautioned against interpreting samples with blood contamination.