Targeted Mass Spectrometric Immunoassay for Detection of Cystatin C Isoforms in Cerebrospinal Fluid

Targeted cerebrospinal fluid (CSF) Mass Spectrometric Immunoassay for cystatin C was developed and applied to a small number of CSF and serum samples obtained from healthy and individuals diagnosed with multiple sclerosis. Cystatin C and its variants were retrieved from the CSF samples via affinity micro columns derivatized with cystatin C antibodies, and were eluted onto MALDI mass spectrometer targets. The resulting mass spectra revealed various levels of cystatin C isoforms in the samples. Truncated Cystatin C isoforms missing 3, 4, 7, 8, 9, 10, 11, 14, 15, and 17 Nterminal amino acid residues were detected. Correlation in the level of truncation between the matched CSF and serum samples was also observed. The mass spectrometric immunoassay provided rapid, high-throughput assessment of cystatin C and its isoforms present in biological fluids.