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

Background: Cerebrospinal fluid (CSF) leaks are potentially life-threatening conditions that can be diagnosed by detection of beta(2)-transferrin using protein electrophoresis. Another less commonly available test is beta-trace protein quantitation using immunoassay. The objectives of this study were to evaluate a new immunofixation-based beta(2)-transferrin test for detection of CSF leaks and to compare it to an existing agarose gel electrophoresis test and beta-trace protein immunoassay. Methods: For method comparison, 63 consecutive samples from physician-ordered beta(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 beta(2)-transferrin immunofixation. A subset of samples (16/63) were analyzed for beta-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 beta(2)-transferrin immunofixation test. Results: The beta(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). beta-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 beta(2)-transferrin immunofixation test based on their migration patterns. However, whole blood samples appeared positive for beta(2)-transferrin at a threshold of similar to 4 g/L hemoglobin. At a cut-off of 3 mg/L, beta-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 beta(2)-transferrin and the beta-trace protein were effective at detecting CSF leaks. Users of the beta(2)-transferrin immunofixation test should be cautioned against interpreting samples with blood contamination.