An exploratory panel of cerebrospinal fluid biomarkers compared to standard diagnostic evaluation in initial demyelinating events suggestive of multiple sclerosis

Background: The diagnosis and the prognostic profile of an initial demyelinating event (IDE) of the central nervous system are not straightforward. The diagnosis of multiple sclerosis (MS) and other IDE etiologies stands on a combination of criteria often requiring a long follow-up to be fulfilled, since single tests with high sensitivity and specificity at the time of IDE presentation are limited. Predictors of disease activity and disability after an IDE are only partially known. Study aim: To investigate the value of tau, 14-3-3 protein and cystatin C as cerebrospinal fluid (CSF) biomarkers of IDEs suggestive of MS, in addition to the prognostic information provided by standard diagnostic evaluation. Methods: CSF samples of a group of subjects with IDEs suggestive of MS were tested for tau, 14-3-3 protein and cystatin C. Clinical, MRI, neurophysiological, and standard CSF analysis data were also collected. For comparison, CSF from patients with neuromyelitis optica (NMO) spectrum disorders, idiopathic acute transverse myelitis (iATM), Creutzfeldt-Jacob disease (CJD) and non-inflammatory/non-neurodegenerative disorders (NINDDs) was also analyzed. CSF biomarkers were tested for diagnostic and prognostic significance. The predictive value of clinical, MRI, and neurophysiological variables was also analyzed in IDE cases. The outcomes of interest for prognostic analysis were: IDE recovery, relapse occurrence, conversion to MS, and subsequent disability level (EDSS score). Results: Forty-six patients with MS-like IDEs, 6 with NMO, 6 with iATM, 8 with CJD and 11 with NINDDs were included. NMO/iATM patients showed significantly higher tau levels compared to both NINDDs and IDEs, even if lower compared to CJD cases. IDE and NMO/iATM patients tested 14-3-3 positive more frequently than NINDDs, although frank 14-3-3 presence was seen much more often in CJD cases. CSF cystatin C concentration did not differ between IDE, NMO/iATM, and NINDDs cases, but was significantly higher in CJD compared to other groups, with the exception of NMO/iATM cases. After a median follow-up of 6.7 (1.5-15.3) years, 39 IDE patients converted to MS, while 7 remained monophasic. CSF tau, 14-3-3 and cystatin C were not correlated to IDE severity and recovery, to risk of MS conversion, or to subsequent disability and relapse rate in MS patients. Severe clinical onset was independently associated with incomplete IDE recovery, the presence of at least 3 periventricular lesions on baseline MRI with relapse risk and conversion to MS, while initial pyramidal involvement and number of relapses with long-term disability in MS cases. Conclusions: The three combined biomarkers provided indications about the underlying pathological processes in distinct CNS disorders. CSF tau showed potential diagnostic utility in differentiating between IDEs suggestive of MS and NMO/iATM. Although the proposed CSF biomarkers panel seems to lack predictive value for IDEs, clinical, MRI and neurophysiological parameters are here confirmed as useful prognostic indicators in this group of patients.