Quantitative and qualitative evaluation of IgG synthesis in 8,947 cerebrospinal fluid samples

Introduction: Increased intrathecal immunoglobulin class G (IgG) synthesis can be found in several neuroinflammatory diseases. Objective: The aim of this study was to analyze quantitative and qualitative methods of intrathecal immunoproduction evaluation. Methods: We retrospectively assessed data from cerebrospinal fluid (CSF) and serum samples sent to Senne Liquor Diagnóstico from 2001 to 2017. Cytological, biochemical, and immunological data were compared between cases with and without oligoclonal bands (OCBs). Comparisons between samples with OCBs (OCB+) and without them (OCB-) were carried out, and the ability to predict the presence of OCBs was assessed with ROC analysis. Results: We included 8,947 samples (2,599 OCB+ samples and 6,348 OCBsamples). CSF lymphocytes and monocytes were significantly associated with the presence of OCB (p < 0.001). All the inflammatory parameters were significantly associated with OCB, and the methods with the highest predictive ability for OCB were IgG index and Reiber diagram [area under the receiver operating characteristic (AUROC) curve = 0.881 and 0.863, respectively]. A small percentage of cases without OCB had high IgG index (9.56%) or Reiber diagram, showing increased IgG production (4.6%). Conclusion: We showed a strong association between OCB and other CSF inflammatory parameters. The presence of cases with increased quantitative CSF IgG synthesis without OCB suggests that both quantitative and qualitative methods should be performed in the evaluation of neuroinflammatory processes.