These findings further support the diagnostic value of intrathecal KFLC synthesis in CIS and MS patients and demonstrate a valid, easier and rater-independent alternative to OCB detection.

Background Free light chains (FLC) have been proposed as diagnostic biomarkers in the cerebrospinal fluid (CSF) of patients with inflammatory central nervous system (CNS) diseases. However, which method to use for determining an intrathecal FLC synthesis has not yet been clarified. The objective of this study was to compare the diagnostic performance of CSF FLC concentration, FLC quotient (QFLC), FLC index and FLC intrathecal fraction (FLCIF). Methods κ- and λ-FLC were measured by nephelometry under blinded conditions in CSF and serum sample pairs of patients with clinically isolated syndrome (CIS; n = 60), multiple sclerosis (MS; n = 60) and other neurological diseases (n = 60) from four different MS centers. QFLC was calculated as the ratio of CSF/serum FLC concentration, the FLC index as QFLC/albumin quotient and the percentage FLCIF by comparing QFLC to a previously empirically determined, albumin quotient-dependent reference limit. Results CSF FLC concentration, QFLC, FLC index and FLCIF of both the κ- and λ-isotype were significantly higher in patients with CIS and MS than in the control group, as well as in oligoclonal bands (OCB) positive than in OCB negative patients. Each parameter was able to identify MS/CIS patients and OCB positivity, however, diagnostic performance determined by receiver operating characteristic (ROC) analyses differed and revealed superiority of FLC index and FLCIF. Conclusions These findings support the diagnostic value of FLC measures that correct for serum FLC levels and albumin quotient, i.e. blood-CSF barrier function.

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SummaryDementia-like syndromes are rare manifestations of Lyme neuroborreliosis. The clinical patterns are summarized using our own cases and case reports from the literature, which were diagnosed as definite Lyme neuroborreliosis according to the European guidelines. The cases disclose signs of subcortical dementia that occur more rapidly than in patients suffering from primary dementia. Gait disturbances early in the disease course is another frequently observed characteristic feature. The response to 2–4 weeks of antibiotic treatment with ceftriaxone was excellent. There were no indications for a prolonged antibiotic treatment. It is essential to be aware of this manifestation of Lyme neuroborreliosis, because early antibiotic treatment will prevent permanent sequelae that may occur throughout the further course of the untreated disease.