Quantifying CSF Mycobacterial Load and Inflammation in TBM

The CSF mycobacterial load was inferred qualitatively by comparing patients with negative versus positive CSF culture, and semiquantitively from the GeneXpert Ct-values as described previously,^{10 (link)} and inferred from CSF M. tuberculosis culture. CSF inflammatory cytokines in 178 Indonesian HIV-negative TBM patients were measured using a multiplex proximity extension assay (Olink) in two batches. Olink uses a multiplex assay that simultaneously recognize 96 target proteins through specific paired-antibodies which are coupled with unique oligonucleotides, for quantitative PCR measurement.^{11 (link)} For each protein, overlapping samples from two batches were fitted in a linear regression model, where the linear components were subsequently extracted, and used as correction factors for batches normalization. In 304 Vietnamese HIV-negative patients, 10 human cytokines were measured in CSF with Luminex multiplex bead array technology (Bio-Rad Laboratories, Hercules, CA).^{4 (link)} CSF total protein was used as proxy for blood-CSF barrier disruption as it showed a near-perfect correlation with the established marker CSF-serum albumin (r²=0.98).^{12 (link)}