Kappa free light chains is a valid tool in the diagnostics of MS: A large multicenter study.

OBJECTIVE: To validate kappa free light chain (KFLC) and lambda free light chain (LFLC) indices as a diagnostic biomarker in multiple sclerosis (MS). METHODS: We performed a multicenter study including 745 patients from 18 centers (219 controls and 526 clinically isolated syndrome (CIS)/MS patients) with a known oligoclonal IgG band (OCB) status. KFLC and LFLC were measured in paired cerebrospinal fluid (CSF) and serum samples. Gaussian mixture modeling was used to define a cut-off for KFLC and LFLC indexes. RESULTS: The cut-off for the KFLC index was 6.6 (95% confidence interval (CI) = 5.2-138.1). The cut-off for the LFLC index was 6.9 (95% CI = 4.5-22.2). For CIS/MS patients, sensitivity of the KFLC index (0.88; 95% CI = 0.85-0.90) was higher than OCB (0.82; 95%CI = 0.79-0.85; p < 0.001), but specificity (0.83; 95% CI = 0.78-0.88) was lower (OCB = 0.92; 95% CI = 0.89-0.96; p < 0.001). Both sensitivity and specificity for the LFLC index were lower than OCB. CONCLUSION: Compared with OCB, the KFLC index is more sensitive but less specific for diagnosing CIS/MS. Lacking an elevated KFLC index is more powerful for excluding MS compared with OCB but the latter is more important for ruling in a diagnosis of CIS/MS.

Peripapillary retinal nerve fibre layer thinning rate as a biomarker discriminating stable and progressing relapsing-remitting multiple sclerosis.

BACKGROUND AND PURPOSE: Peripapillary retinal nerve fibre layer (pRNFL) thickness is a strong candidate as a biomarker of axonal degeneration in multiple sclerosis (MS). The aim was to determine a cut-off value of pRNFL thinning rates in relapsing-remitting MS (RRMS) to discriminate between stable and progressing patients. METHODS: In this 3-year prospective longitudinal study on 141 RRMS patients, annual pRNFL thinning rates (aLpRNFL) were determined by individual linear regression models. The best possible cut-off value discriminating clinically progressing (physical progression or cognitive decline) and stable patients was defined by receiver operating characteristic analysis. Cut-off values were validated using a multivariate logistic regression model. RESULTS: Average aLpRNFL in progressing patients (2.4 µm, SD 2.1) was significantly higher compared to stable patients (0.5 µm, SD 1.2, P < 0.001). At a predefined specificity of 90%, aLpRNFL >1.5 µm was able to distinguish between stable and progressing RRMS with a sensitivity of 76.1%. aLpRNFL >1.5 µm was associated with a 15-fold increased risk of clinically progressing MS (P < 0.001). CONCLUSIONS: A cut-off of aLpRNFL discriminating clinically progressing and stable RRMS was identified. After validation in independent cohorts, this cut-off could be used as a biomarker of axonal degeneration supporting disease monitoring in daily clinical routine.

Cerebrospinal fluid:serum glucose ratio in the ventricular and lumbar compartments: implications for clinical practice.

BACKGROUND AND PURPOSE: Calculation of the cerebrospinal fluid:serum glucose (CSF:SGlu ) ratio is part of the routine cerebrospinal fluid (CSF) work-up. Reference values have been defined for lumbar CSF, but are lacking for ventricular CSF. The objective of this study was to investigate whether the CSF:SGlu ratio is similar in lumbar and ventricular compartments, and to determine cut-off values for CSF:SGlu ratio in ventricular CSF. METHODS: We included CSF samples that were collected by either lumbar puncture or ventricular drainage, with a red blood cell count <500/µL, normal white blood cell count and age-related normal total protein content, with simultaneously withdrawn serum sample and time to laboratory processing of ≤2 h. This resulted in 1808 sample pairs. Glucose concentrations in CSF and serum were measured by enzymatic spectrophotometry. RESULTS: The CSF:SGlu ratio was similar in ventricular and lumbar compartments after controlling for age, sex, time between sample withdrawal and laboratory processing, CSF white blood cell and red blood cell count, CSF total protein and serum glucose concentration using a multiple linear regression model. Lower limits for CSF:SGlu ratio in the ventricular compartment, defined as 5th percentile, were 0.51 for patients with serum glucose concentration < 100 mg/dL, 0.45 for those with serum glucose concentration ≥ 100 mg/dL and <150 mg/dL, and 0.36 for those with serum glucose concentration ≥150 mg/dL. CONCLUSIONS: The CSF:SGlu ratio was similar in the ventricular and lumbar compartments, and depended mainly on time to laboratory processing and absolute serum glucose levels. Previously established lower limits for CSF:SGlu ratio in lumbar CSF can be also applied for ventricular CSF.

Combined evaluation of personality, risk and coping in MS patients: A step towards individualized treatment choice - The PeRiCoMS-Study I.

BACKGROUND: Multiple sclerosis (MS) is a chronic inflammatory neurological disease requiring disease-modifying treatment (DMT). To provide patients with the optimal individual therapeutic option, treatment recommendations should be based not only on individual disease course and DMT specific benefit-risk estimates, but also on patient's individual characteristics such as personality, risk attitude and coping strategies. However, these characteristics are difficult to objectify in clinical routine practice without the support of appropriate evaluation instruments. OBJECTIVE: To identify and to assemble an objective test battery measuring personality, risk attitude and coping strategies in MS patients. METHODS: A comprehensive literature search was performed to obtain all questionnaires assessing personality, risk attitude and coping strategies. Availability in German language, validation in a published normative collective and a reliability of >0.70 were required for our purposes. Based on these criteria, we chose the Big-Five-Personality Test, UPPS Impulsive Behaviour Scale, Domain-Specific Risk-Taking scale (DOSPERT), Brief-COPE and Stress & Coping Inventory (SCI). Results were compared to published normative controls of the respective questionnaires. RESULTS: Out of 22 MS patients (7 males, 15 females) participating in this study, 19 (86.4%) completed all questionnaires. The median completion time was 45min (min-max range: 25-60min). The median scores of the MS group were within the average range of published control samples in all questionnaires. CONCLUSIONS: We report that traits of personality, risk attitude and coping strategies can be effectively and feasibly tested in MS patients by the instruments used in our exploratory study. There were no differences between MS patients and healthy controls, thus enabling assessment without being influenced by the diagnosis of MS. After validation in a larger cohort the "PeRiCoMS"-battery will be useful as another step towards a more individualized shared-decision-making in every day routine practice.

Quantitation of intrathecal immunoglobulin synthesis - a new empirical formula.

BACKGROUND AND PURPOSE: Intrathecal immunoglobulin (Ig) synthesis occurs in various chronic inflammatory neurological diseases. Different formulae have been developed for quantitative determination of Ig synthesis within the cerebrospinal fluid (CSF) compartment. The hyperbolic formula of Reiber is frequently used which, however, returns a considerable number of false positive results in empirical observations. METHODS: A computerized database of more than 19 000 paired CSF and serum samples was screened for patients presumed negative for local Ig synthesis and a new formula characterizing this collective was calculated. The validity of this formula was confirmed by several validation steps. RESULTS: A cohort of 1173 patients with normal CSF findings was used for quantile regression. The 97.5th quantile of the formula Qlim(IgX)=a×Qalbb was considered as the cut-off curve for intrathecal Ig synthesis using different constants a and b for IgG, IgA and IgM. Compared to the Reiber formula, a lower level of false positive results was produced especially for IgM and IgA which was confirmed in a separate clinically well defined validation cohort. In 77 patients with discrepant findings between Reiber and our formula no specific diagnoses were found confirming the low diagnostic value of borderline Ig synthesis. CONCLUSIONS: A new approximation formula was developed for determination of intrathecal Ig synthesis which produces fewer false positive results without reducing diagnostic sensitivity.

Supratentorial white matter blurring associated with voltage-gated potassium channel-complex limbic encephalitis.

INTRODUCTION: Limbic encephalitis (LE) associated with voltage-gated potassium channel-complex antibodies (VGKC-LE) is frequently non-paraneoplastic and associated with marked improvement following corticosteroid therapy. Mesial temporal lobe abnormalities are present in around 80 % of patients. If associated or preceded by faciobrachial dystonic seizures, basal ganglia signal changes may occur. In some patients, blurring of the supratentorial white matter on T2-weighted images (SWMB) may be seen. The purpose of this study was to evaluate the incidence of SWMB and whether it is specific for VGKC-LE. METHODS: Two experienced neuroradiologists independently evaluated signal abnormalities on FLAIR MRI in 79 patients with LE while unaware on the antibody type. RESULTS: SWMB was independently assessed as present in 10 of 36 (28 %) compared to 2 (5 %) of 43 non-VGKC patients (p = 0.009). It was not related to the presence of LGI1 or CASPR2 proteins of VGKC antibodies. MRI showed increased temporomesial FLAIR signal in 22 (61 %) VGKC compared to 14 (33 %) non-VGKC patients (p = 0.013), and extratemporomesial structures were affected in one VGKC (3 %) compared to 11 (26 %) non-VGKC patients (p = 0.005). CONCLUSION: SWMB is a newly described MRI sign rather specific for VGKC-LE.

Standardizing terms, definitions and concepts for describing and interpreting unwanted immunogenicity of biopharmaceuticals: recommendations of the Innovative Medicines Initiative ABIRISK consortium.

Biopharmaceuticals (BPs) represent a rapidly growing class of approved and investigational drug therapies that is contributing significantly to advancing treatment in multiple disease areas, including inflammatory and autoimmune diseases, genetic deficiencies and cancer. Unfortunately, unwanted immunogenic responses to BPs, in particular those affecting clinical safety or efficacy, remain among the most common negative effects associated with this important class of drugs. To manage and reduce risk of unwanted immunogenicity, diverse communities of clinicians, pharmaceutical industry and academic scientists are involved in: interpretation and management of clinical and biological outcomes of BP immunogenicity, improvement of methods for describing, predicting and mitigating immunogenicity risk and elucidation of underlying causes. Collaboration and alignment of efforts across these communities is made difficult due to lack of agreement on concepts, practices and standardized terms and definitions related to immunogenicity. The Innovative Medicines Initiative (IMI; www.imi-europe.org), ABIRISK consortium [Anti-Biopharmaceutical (BP) Immunization Prediction and Clinical Relevance to Reduce the Risk; www.abirisk.eu] was formed by leading clinicians, academic scientists and EFPIA (European Federation of Pharmaceutical Industries and Associations) members to elucidate underlying causes, improve methods for immunogenicity prediction and mitigation and establish common definitions around terms and concepts related to immunogenicity. These efforts are expected to facilitate broader collaborations and lead to new guidelines for managing immunogenicity. To support alignment, an overview of concepts behind the set of key terms and definitions adopted to date by ABIRISK is provided herein along with a link to access and download the ABIRISK terms and definitions and provide comments (http://www.abirisk.eu/index_t_and_d.asp).

Early detection of neutralizing antibodies to interferon-beta in multiple sclerosis patients: binding antibodies predict neutralizing antibody development.

BACKGROUND: Neutralizing antibodies (NAb) affect efficacy of interferon-beta (IFN-b) treatment in multiple sclerosis (MS) patients. NAbs evolve in up to 44% of treated patients, usually between 6-18 months on therapy. OBJECTIVES: To investigate whether early binding antibody (BAb) titers or different IFN-b biomarkers predict NAb evolution. METHODS: We included patients with MS or clinically isolated syndrome (CIS) receiving de novo IFN-b treatment in this prospective European multicenter study. Blood samples were collected at baseline, before and after the first IFN-b administration, and again after 3, 12 and 24 months on that therapy; for determination of NAbs, BAbs, gene expression of MxA and protein concentrations of MMP-9, TIMP-1, sTRAIL, CXCL-10 and CCL-2. RESULTS: We found that 22 of 164 (13.4%) patients developed NAbs during a median time of 23.8 months on IFN-b treatment. Of these patients, 78.9% were BAb-positive after 3 months. BAb titers ≥ 1:2400 predicted NAb evolution with a sensitivity of 74.7% and a specificity of 98.5%. Cross-sectionally, MxA levels were significantly diminished in the BAb/NAb-positive samples; similarly, CXCL-10 and sTRAIL concentrations in BAb/NAb-positive and BAb-positive/NAb-negative samples, respectively, were also diminished compared to BAb/NAb-negative samples. CONCLUSIONS: BAb titers reliably predict NAbs. CXCL-10 is a promising sensitive biomarker for IFN-b response and its abrogation by anti-IFN-b antibodies.

High-dose intravenous interferon-beta in multiple sclerosis patients with high-titer neutralizing antibodies (HINABS II) - A pilot study.

BACKGROUND: Neutralizing antibodies (NAb) against interferon-beta (IFNß) affect its treatment efficacy. So far, there are no anti-NAb strategies available. OBJECTIVES: To investigate if the repeated administration of high-dose IFNß-1b intravenous in NAb positive multiple sclerosis (MS) patients induces tolerance and establishes IFNß bioavailability as measured by the induction of myxovirus protein A (MxA). METHODS: Nine MS patients with NAb titers >500 10-fold reduction units (TRU) received 1500µg IFNß-1b intravenously once weekly over three months. Blood samples were collected at screening, monthly during the treatment period (before and four hours after IFNß administration), and at follow-up after 6 months for determination of NAbs and MxA expression. RESULTS: Median NAb titer at baseline was 1429TRU. NAb titers determined before each infusion did not significantly change over the treatment period and were not different at follow-up compared to baseline. However, NAb titers were significantly decreased four hours after IFNß infusions (by roughly 50%) and MxA mRNA levels were significantly elevated reaching a median value of 206. CONCLUSIONS: Weekly intravenous administration of IFNß in patients with high NAb titers established its bioavailability, but failed to induce tolerance towards IFNß.

Olfactory threshold is impaired in early, active multiple sclerosis.

BACKGROUND: Olfactory dysfunction has been reported in multiple sclerosis (MS). However, to date no data are available on different qualities of olfactory function, namely odour identification, odour discrimination and odour perception threshold. OBJECTIVE: To assess different qualities of olfactory function in patients with MS and correlate these with demographic data, clinical data, depression, quality of life and cognitive functions. METHODS: In this cross-sectional study, 50 patients with MS or clinically isolated syndrome and 30 healthy controls were included. Olfactory function was measured using the Sniffin' Sticks test. RESULTS: The scores for odour identification (p = 0.001), odour perception threshold (p = 0.037) and the combined score of odour identification, discrimination and perception threshold (TDI, p = 0.002) were significantly lower in MS. Hyposmia for identification (p = 0.0017), threshold (p = 0.017) and TDI score (p = 0.0014) was more frequent in MS. Olfactory threshold was impaired in patients who were clinically active in the previous year (p = 0.026) and in patients with a disease duration less than 2 years (p = 0.0093). Identification score was negatively correlated with disease duration (p = 0.0017). Olfactory function was not associated with disability, depression or quality of life. CONCLUSIONS: We report evidence for qualitatively distinct hyposmia in MS, with increased smell threshold in the early inflammatory phases of the disease and impaired identification with a more widespread chronic disease.

Decision-making for and impact of early immunomodulatory treatment: the Austrian Clinically Isolated Syndrome Study (ACISS).

BACKGROUND AND PURPOSE: When to start disease-modifying treatment (DMT) in patients with a clinically isolated syndrome (CIS) requires individual weighing of benefits versus possible burden of side effects and costs. How this occurs in a routine setting is barely known. The aim of the study was to investigate the decision-making process regarding immediate or later DMT and the ensuing impact on CIS patients in Austria. METHODS: Demographic and (para) clinical characteristics of 296 CIS patients were recorded in 29 multiple sclerosis (MS) centres, and the patients' overall condition was rated on a visual analogue scale (VAS). Clinical follow-up and VAS ratings were repeated at 6-month intervals over 2 years. The decision for initiation of DMT was at the physician's and patient's discretion. RESULTS: In 29% of patients, DMT was started within 3 months and this decision was independently associated with a T2-lesion number >or=9 on MRI and a worse VAS rating by the physician. DMT initiation in the subsequent 6 months was additionally associated with the presence of oligoclonal bands and rarely occurred thereafter. Adapted to the clinical course, later treatment was associated with the highest rate of conversion to clinically definite MS and greatest disability after 2 years whilst never treated patients fared best. Patient VAS ratings significantly improved during follow-up independently of treatment decisions. CONCLUSION: The management of Austrian CIS patients relies strongly on MRI findings and the physicians' interpretation of the patients' overall situation which, after 2 years, depends primarily on the course of the disease.

A consensus protocol for the standardization of cerebrospinal fluid collection and biobanking.

There is a long history of research into body fluid biomarkers in neurodegenerative and neuroinflammatory diseases. However, only a few biomarkers in CSF are being used in clinical practice. One of the most critical factors in CSF biomarker research is the inadequate powering of studies because of the lack of sufficient samples that can be obtained in single-center studies. Therefore, collaboration between investigators is needed to establish large biobanks of well-defined samples. Standardized protocols for biobanking are a prerequisite to ensure that the statistical power gained by increasing the numbers of CSF samples is not compromised by preanalytical factors. Here, a consensus report on recommendations for CSF collection and biobanking is presented, formed by the BioMS-eu network for CSF biomarker research in multiple sclerosis. We focus on CSF collection procedures, preanalytical factors, and high-quality clinical and paraclinical information. The biobanking protocols are applicable for CSF biobanks for research targeting any neurologic disease.

A type I interferon signature in monocytes is associated with poor response to interferon-beta in multiple sclerosis.

The effect of interferon-beta in multiple sclerosis is modest and many patients do not respond to treatment. To date, no single biomarker reliably correlates with responsiveness to interferon-beta in multiple sclerosis. In the present study, genome-wide expression profiling was performed in peripheral blood mononuclear cells from 47 multiple sclerosis patients treated with interferon-beta for a minimum of 2 years and classified as responders and non-responders based on clinical criteria. A validation cohort of 30 multiple sclerosis patients was included in the study to replicate gene-expression findings. Before treatment, interferon-beta responders and non-responders were characterized by differential expression of type I interferon-induced genes with overexpression of the type interferon-induced genes in non-responders. Upon treatment the expression of these genes remained unaltered in non-responders, but was strongly upregulated in responders. Functional experiments showed a selective increase in phosphorylated STAT1 levels and interferon receptor 1 expression in monocytes of non-responders at baseline. When dissecting this type I interferon signature further, interferon-beta non-responders were characterized by increased monocyte type I interferon secretion upon innate immune stimuli via toll-like receptor 4, by increased endogenous production of type I interferon, and by an elevated activation status of myeloid dendritic cells. These findings indicate that perturbations of the type I interferon signalling pathway in monocytes are related to lack of response to interferon-beta, and type I interferon-regulated genes may be used as response markers in interferon-beta treatment.

EFNS guidelines on disease-specific CSF investigations.

We reviewed the literature for disease-specific markers in cerebrospinal fluid (CSF) and evaluated their diagnostic and prognostic relevance in neurological diseases. High tau protein in combination with low amyloid beta levels has a high sensitivity (80%) and specificity (90%) for Alzheimer's disease (AD) against normal aging and can predict conversion of mild cognitive impairment to AD. The detection of 14-3-3 has a high sensitivity (80-90%) and specificity (90%) for the diagnosis of CJD. Low or undetectable CSF hypocretin-1 (orexin-1) levels constitute a diagnostic biomarker for narcolepsy with cataplexy. Detection of beta-2-transferrin indicates CSF contamination in oto- and rhinorrhoe with a sensitivity of > 79% at a specificity of 95% similar to the beta-trace protein (sensitivity > 90%, specificity 100%). However, beta-trace protein is faster and cheaper to perform. Possible future biomarkers are: elevated levels of vascular endothelial growth factor are relatively sensitive (51-100%) and specific (73-100%) for leptomeningeal metastases from solid tumors and are associated with a poor prognosis in this condition. Elevated CSF neurofilament (Nf) levels probably reflect acute neuronal degeneration. The prognostic value of CSF Nf levels is highest in acute conditions such as subarachnoid hemorrhage, acute optic neuritis and neuromyelitis optica.

High-dose intravenous interferon beta in patients with neutralizing antibodies (HINABS): a pilot study.

BACKGROUND: Neutralizing antibodies (NABs) against interferon beta (IFNbeta) are associated with a loss of IFNbeta bioactivity and clinical effectiveness. To date, there are no anti-NAB strategies available. The primary objective of this trial was to investigate whether intravenous IFNbeta-1b can restore bioactivity in NAB-positive patients with MS. METHODS: NAB-positive patients with MS were treated with 8 MIU IFNbeta-1b s.c., 8 MIU i.v., and 16 MIU i.v. Each application was preceded by a wash-out period of 1 week. Blood samples were collected before, 3, 12, and 24 h after each administration. Myxovirus protein A (MxA) RNA and protein levels were determined. The study has been approved by the local ethics committee. RESULTS: Five patients completed the study. NAB titers ranged from 42 to 4482 neutralizing units. Median MxA protein (1821, range 12-3234) and RNA (2186, range 114-7525) area under the curve levels for the four measurements at each IFNbeta injection were significantly higher after i.v. application of 16 MIU as compared with both 8-MIU dosages, which were 743 (0-2709) for MxA protein after 8 MIU i.v. and 254 (0-1200) after s.c., and 1763 (25-7188) for MxA RNA after 8 MIU i.v., and 557 (5-2265) after s.c. applications. NAB titers decreased significantly and transiently after infusion of 16 MIU IFNbeta-1b but not after both forms of 8 MIU applications. Typical side effects could be controlled by paracetamol. No allergic reaction was observed. DISCUSSION: The results indicate that i.v. administration of IFNbeta can restore bioavailability of IFNbeta in patients with NABs.

Smoking is a risk factor for early conversion to clinically definite multiple sclerosis.

BACKGROUND: Cigarette smoking increases the risk for development of multiple sclerosis and modifies the clinical course of the disease. In this study, we determined whether smoking is a risk factor for early conversion to clinically definite multiple sclerosis after a clinically isolated syndrome. METHODS: We included 129 patients with a clinically isolated syndrome, disseminated white-matter lesions on brain magnetic resonance imaging, and positive oligoclonal bands in the cerebrospinal fluid. The patients' smoking status was obtained at the time of the clinically isolated syndrome. RESULTS: During a follow-up time of 36 months, 75% of smokers but only 51% of non-smokers developed clinically definite multiple sclerosis, and smokers had a significantly shorter time interval to their first relapse. The hazard ratio for progression to clinically definite multiple sclerosis was 1.8 (95% confidence interval, 1.2-2.8) for smokers compared with non-smokers (P = 0.008). CONCLUSIONS: Smoking is associated with an increased risk for early conversion to clinically definite multiple sclerosis after a clinically isolated syndrome, and our results suggest that smoking is an independent but modifiable risk factor for disease progression of multiple sclerosis. Therefore, it should be considered in the counseling of patients with a clinically isolated syndrome.

MxA protein--an interferon beta biomarker in primary progressive multiple sclerosis patients.

BACKGROUND AND PURPOSE: Interferon beta (IFNbeta) preparations have some effect on the progressive phase of multiple sclerosis (MS). This limited effect might be partially because of a certain number of IFNbeta non-responders. Myxovirus resistance protein A (MxA)--a marker of IFNbeta bioactivity--was correlated with the clinical response during an uncontrolled trial, investigating the safety of IFNbeta-1b in primary progressive (PPMS) patients. METHODS: Twenty PPMS were treated with IFNbeta-1b (s.c.) for 1 year. Blood samples were taken before and 1, 2, 3, 6, 9, 12, and 15 months after treatment initiation and MxA protein levels were measured. Patients were clinically evaluated by EDSS and the more sensitive Incapacity Status Scale (ISS) and stratified in a stable and a progressing group. RESULTS: Using ISS criteria, 11 patients remained stable and nine patients progressed during treatment. The mean area under the curve of log MxA levels during treatment were significantly higher in stable than in progressing patients (10.87 vs. 5.99; P = 0.002). CONCLUSION: A good biological response to IFNbeta might be associated with a better clinical effect of this drug and could be helpful in future clinical studies for early identification of treatment responders.

Comparative study of four different assays for the detection of binding antibodies against interferon-beta.

BACKGROUND: Binding antibodies (BAB) against interferon-beta (IFNbeta) are often determined as screening assays before performing an expensive and elaborate neutralizing antibody (NAB) test. METHODS: In this study, we compared four BAB tests, a western blot (WB), a direct binding enzyme-linked immunosorbent assay (ELISA) (dELISA), a capture ELISA (cELISA), and a commercial enzyme immuno-assay (EIA) in 325 multiple sclerosis patients with and without neutralizing antibodies to evaluate the sensitivity and specificity to detect NAB by receiver operating characteristics analysis. RESULTS: The area under the curve (AUC) values were 0.907 for the dELISA, 0.925 for the cELISA, and 0.776 for the EIA (P < 0.0001 for all). At a sensitivity of 95%, the specificity was approximately 30% in the dELISA, 55% in the cELISA, and 13% in the EIA. The WB as a qualitative BAB detection method had a given sensitivity of 97% and a specificity of 55%. There was a strong and significant correlation between high NAB titers (>500 neutralizing units [NU]) and titers obtained by all quantitative BAB assays. However, low to medium NAB titers (20-500 NU) did not significantly correlate with BAB titers. CONCLUSION: We conclude that the cELISA seems to be most suitable for NAB screening, but BAB titers cannot reliably predict NAB titers.