Validation of ELISA assays for the calculation of FLC indices for the diagnosis of intrathecal immunoglobulin synthesis.

OBJECTIVES: Define the cutoff thresholds of the Kappa (K) and Lambda (L) free light chains (FLC) indices for the detection of intrathecal immunoglobulin synthesis (IIS) using the new K and L FLC ELISA from SEBIA. The reference technique, which is not readily standardized between laboratories, is based on the demonstration of oligoclonal banding (OCB) in cerebrospinal fluid (CSF) which is absent in serum. For the past 6 years, we have also routinely calculated the K FLC index using The Binding Site (TBS) reagents on an Optilite instrument, an approach increasingly used as an alternative and/or a complement to electrophoretic analysis. METHODS: We analyzed 391 serum/CSF pairs divided into three groups. The first group were cases without OCB and with normal albumin CSF/serum ratio (n=174). The second group were cases with specific OCB (n=73). The last group included patients with increased albumin CSF/sera ratio without OCB (n=142). RESULTS: Analysis of the first group determined that the cutoffs for detection of IIS are respectively 2.55 and 1.02 for the K FLC and L FLC indices. Of the 73 cases with IIS, only 2 had a K FLC index below this threshold (sensitivity of 97.26%), while 16 out of 73 cases (78.08%) and 13 out of 72 cases (81.94%) had an IgG and L FLC index below the cutoffs, respectively. Additionally, we illustrate equivalent performances for prediction of the presence of OCB between SEBIA and TBS methods. CONCLUSIONS: Sebia K FLC and L FLC assays are adequate alternative methods for the diagnosis of IIS.

Could clinical profile influence CSF biomarkers in early-onset Alzheimer disease?

In common forms of Alzheimer disease (AD), anterograde memory impairment is the first deficit to occur. However, the disease, especially in its presenile forms, may also manifest itself through initial deficits that are predominantly of a nonmemory type. These distinct clinical profiles, which reflect the distinct topography of the underlying pathologic processes, may also differ in terms of their cerebrospinal fluid (CSF) markers. The aim of this study was to assess the levels of total tau, phosphorylated tau, and amyloid-beta 42 peptide in the CSF of "atypical" (nonmemory) early-onset AD patients. CSF biomarkers were evaluated in 22 atypical patients, and compared with those from a group of 13 "typical" patients, with a memory onset form of the disease. Our results show that independently of age, disease duration, education level, and clinical severity indices, patients with an atypical onset have significantly higher levels of total tau in the CSF (P=0.023). These findings indicate that an assessment of CSF biomarkers may be of particular use in the clinical diagnosis of "atypical-onset" forms of early-onset AD in which the initial symptoms involve language and visuospatial abilities rather than memory. In addition, they highlight the heterogeneity of pathologic processes in AD, suggesting more intense degeneration in the forms of the disease that primarily involve neocortical structures.

Predictive factors of efficacy of rituximab in patients with anti-MAG neuropathy.

OBJECTIVE: To identify factors associated with efficacy of rituximab (RTX) infusions in patients with anti-myelin associated glycoprotein (MAG) neuropathy. METHODS: 33 patients with anti-MAG neuropathy treated with RTX were retrospectively evaluated. All patients underwent neurological, biological, and electrophysiological examinations. Good response was defined as an improvement of at least one point of the Overall Neuropathy Limitation Scale (ONLS) at 6months or at the last follow-up. Disease evolution was defined as sub-acute if the ONLS increased by at least 2 points the year before therapy. RESULTS: Ten patients (30%) were improved 6months after RTX and 6/20 (30%) at the last follow-up (mean 42months). Response to RTX was significantly associated with subacute evolution and proximal weakness of the lower limbs at the onset of disease. Improvement was not correlated with electrophysiological data and anti-MAG antibodies titers. DISCUSSION: This study suggests that RTX may be efficacious in a sub-population of patients with anti-MAG neuropathy, particularly in those with proximal weakness of the lower limbs or sub-acute evolution.