Neuronal uptake of anti-Hu antibody, but not anti-Ri antibody, leads to cell death in brain slice cultures.

BACKGROUND: Anti-Hu and anti-Ri antibodies are paraneoplastic immunoglobulin (Ig)G autoantibodies which recognize cytoplasmic and nuclear antigens present in all neurons. Although both antibodies produce similar immunohistological labeling, they recognize different neuronal proteins. Both antibodies are associated with syndromes of central nervous system dysfunction. However, the neurological deficits associated with anti-Hu antibody are associated with neuronal death and are usually irreversible, whereas neurological deficits in patients with anti-Ri antibody may diminish following tumor removal or immunosuppression. METHODS: To study the effect of anti-Hu and anti-Ri antibodies on neurons, we incubated rat hippocampal and cerebellar slice cultures with anti-Hu or anti-Ri sera from multiple patients. Cultures were evaluated in real time for neuronal antibody uptake and during prolonged incubation for neuronal death. To test the specificity of anti-Hu antibody cytotoxic effect, anti-Hu serum IgG was incubated with rat brain slice cultures prior to and after adsorption with its target Hu antigen, HuD. RESULTS: We demonstrated that: 1) both anti-Hu and anti-Ri antibodies were rapidly taken up by neurons throughout both cerebellum and hippocampus; 2) antibody uptake occurred in living neurons and was not an artifact of antibody diffusion into dead cells; 3) intracellular binding of anti-Hu antibody produced neuronal cell death, whereas uptake of anti-Ri antibody did not affect cell viability during the period of study; and 4) adsorption of anti-Hu antisera against HuD greatly reduced intraneuronal IgG accumulation and abolished cytotoxicity, confirming specificity of antibody-mediated neuronal death. CONCLUSIONS: Both anti-Hu and anti-Ri antibodies were readily taken up by viable neurons in slice cultures, but the two antibodies differed markedly in terms of their effects on neuronal viability. The ability of anti-Hu antibodies to cause neuronal death could account for the irreversible nature of paraneoplastic neurological deficits in patients with this antibody response. Our results raise questions as to whether anti-Ri antibody might initially induce reversible neuronal dysfunction, rather than causing cell death. The ability of IgG antibodies to access and react with intracellular neuronal proteins could have implications for other autoimmune diseases involving the central nervous system.

Dermatitis herpetiformis sera or goat anti-transglutaminase-3 transferred to human skin-grafted mice mimics dermatitis herpetiformis immunopathology.

Dermatitis herpetiformis (DH) is characterized by deposition of IgA in the papillary dermis. However, indirect immunofluorescence is routinely negative, raising the question of the mechanism of formation of these immune deposits. Sárdy et al. (2002. J. Exp. Med. 195: 747-757) reported that transglutaminase-3 (TG3) colocalizes with the IgA. We sought to create such deposits using passive transfer of Ab to SCID mice bearing human skin grafts. IgG fraction of goat anti-TG3 or control IgG were administered i.p. to 20 mice. Separately, sera from seven DH patients and seven controls were injected intradermally. Biopsies were removed and processed for routine histology as well as direct immunofluorescence. All mice that received goat anti-TG3 produced papillary dermal immune deposits, and these deposits reacted with both rabbit anti-TG3 and DH patient sera. Three DH sera high in IgA anti-TG3 also produced deposits of granular IgA and TG3. We hypothesize that the IgA class anti-TG3 Abs are directly responsible for the immune deposits and that the TG3 is from human epidermis, as this is its only source in our model. These deposits seem to form over weeks in a process similar to an Ouchterlony immunodiffusion precipitate. This process of deposition explains the negative indirect immunofluorescence results with DH serum.

Presence of anti-gp210 or anti-sp100 antibodies in AMA-positive patients may help support a diagnosis of primary biliary cholangitis.

BACKGROUND: Anti-mitochondrial antibody (AMA) positivity is not always associated with primary biliary cholangitis (PBC). We aimed to determine the additional value of anti-sp100 or anti-gp210 antibody in AMA-positive patients for PBC. METHODS: Patients (n = 190) and healthy donors (n = 50) were evaluated for AMA, anti-gp210 and anti-sp100 antibodies by ELISA. Antibody frequencies in cohorts and performance characteristics in some patients categorized as 'definitive-', 'probable-', and 'no PBC' were determined following review of their charts. RESULTS: Of the patients (n = 190), 38.4% were AMA-positive (n = 73) and 61.6% AMA-negative (n = 117). Frequency of anti-sp100 or anti-gp210 antibody was 17.8%, 2.6%, and 0% in AMA-positive, AMA-negative and healthy controls, respectively. Clinical data was available for 63 of 73 AMA-positive patients with 28.6%, 22.2%, and 49.2% categorized as definite, probable, and no PBC, respectively. Patients with definite PBC had higher mean levels of AMA and frequencies of sp100 or gp210 antibody compared to other groups. Sensitivities were low (anti-sp100: 18.8% and anti-gp210: 16.7%) with specificities above 98.0% for both. CONCLUSION: AMA-positive patients positive for anti-sp100 or anti-gp210 antibody were more likely to have a diagnosis of definite or probable PBC than those with AMA alone. Use of all tests is likely to improve characterization of patients at-risk for PBC.

Novel screening assay performance in pediatric celiac disease and adult dermatitis herpetiformis.

OBJECTIVES: : Several serologic assays are commercially available to aid in the diagnosis of gluten-sensitive enteropathy (GSE). Our objective in this study was to assess the performance of a novel combined antigen-screening assay for GSE. PATIENTS AND METHODS: : Deidentified sera from 111 pediatric patients suspected of having celiac disease (CD), 130 adults diagnosed with dermatitis herpetiformis (DH), and 77 pediatric and 49 adult normal controls were included in the study. Sera from 10 patients submitted to our laboratory for GSE testing with IgA deficiency and IgG antibodies against 1 or more of the traditional serologic markers associated with GSE were also included. All sera were screened for antibodies (IgA and IgG) against tissue transglutaminase (tTG) and deamidated gliadin peptides (DGP) by enzyme immunoassay (EIA) in a single test well. In addition, all sera were assessed for each individual marker and isotype using separate EIAs. RESULTS: : The IgA/IgG anti-tTG/DGP EIA screen was 92.6% sensitive and 94.3% specific in pediatric CD and detected 1 patient (Marsh 3c) who was IgA anti-tTG negative; this patient was not IgA deficient (<7.0 mg/dL). All 10 IgA-deficient sera gave positive results by the tTG/DGP EIA screen. Sensitivity and specificity of the tTG/DGP EIA screen in retrospective and prospective DH were 65% and 100% versus 62% and 100%, respectively. CONCLUSIONS: : The new IgA/IgG anti-tTG/DGP EIA screen was slightly more sensitive than IgA anti-tTG alone in pediatric CD. This novel screening assay may allow the current recommendation of measuring total serum IgA in suspected GSE patients to be eliminated.

Myth and reality: practical test system for the measurement of anti-DNA antibodies in the diagnosis of systemic lupus erythematosus (SLE).

The myth persists that only the labor intensive Farr radioimmunoassay and Crithidia luciliae immunofluorescence (CL-IFA) are systemic lupus erythematosus (SLE)-specific tests. We compared them to ELISA with bacteriophage lambda DNA (EL-dsDNA) and denatured calf thymus DNA (EL-ssDNA). By percentile ranking, the specificity cut-off level was set both out of clinical context (SOCC) on 100 blood bank donors, and in clinical context (SICC) on 100 patients with either rheumatoid arthritis or scleroderma (50/50). Clinical sensitivity was calculated on 100 random SLE patients. At 95% SICC, the sensitivity of Farr, CL-IFA, EL-dsDNA, and EL-ssDNA was similar (95%CI): 76% (66-84), 76% (66-84), 63% (53-72), and 75% (65-83), respectively; 87% of the patients were positive by at least one method and 55%by all methods. At 99% SICC, the sensitivity was also similar (95% CI): 57% (47-67), 47% (37-57), 58% (47-67), and 43% (33-53), respectively. The areas under ROC curve were similar (95% CI) when patients were used as controls for specificity. At 99% SOCC, EL-ssDNA identified 89% positive, 2 negative but positive by another method at 95% SICC, and 9 negative (i.e. 89/2/9), followed by CL-IFA (80/6/14), Farr (76/12/12), and EL-dsDNA (64/23/13). Thus, at relatively low cost and easy automation, under the same conditions of specificity, the two ELISA tests combined were at least as good, if not superior, to CL-IFA or Farr: they showed similar clinical sensitivity and also identified more patients with anti-DNA antibodies.

Diagnostic performance of phospholipid-specific assays for the evaluation of antiphospholipid syndrome.

The diagnostic performance of commercially available nonstandard antiphospholipid (aPL) assays for the evaluation of antiphospholipid syndrome (APS) is unknown. In 62 patients with APS, 88 with recurrent pregnancy loss, 50 healthy blood donors, and 24 women with one or more successful pregnancies, we measured antiphosphatidic acid (aPA), antiphosphatidyl-choline (aPC), antiphosphatidylethanolamine (aPE), antiphosphatidylglycerol (aPG), antiphosphatidylinositol (aPI), and antiphosphatidyl-serine (aPS) IgG and IgM antibodies from 2 manufacturers. We computed the areas under the curve (AUC), sensitivities, specificities, positive and negative predictive values, and 95% confidence intervals to assess diagnostic performance. The AUC analyses of the IgM assays demonstrated significant differences (P < .01) for all markers except aPC, whereas the IgG markers showed comparable performance for most assays with the exception of aPE (P < .01) and aPS (P = .02) antibodies. Overall, the combined sensitivity of the aPL assays differed significantly between manufacturers and did not improve the diagnostic yield for APS.

Antibodies to small ubiquitin-like modifier activating enzyme are associated with a diagnosis of dermatomyositis: results from an unselected cohort.

The aim of this study was to examine the frequency and significance of antibodies targeting the small ubiquitin-like modifier 1 activating enzyme (SAE) in patients under serologic evaluation for idiopathic inflammatory myopathies. Patient sera (n = 17) recognizing bands at approximately 40 (SAE1) and 90 (SAE2) kDa were identified in 6445 consecutive samples for myositis autoantibody evaluation by immunoprecipitation (IP) of S35-labeled K562 cell lysate. All 17 positive samples, 176 disease, and 67 healthy controls were evaluated for SAE1 antibodies using a line immunoblot assay (LIA). Clinical data of SAE antibody-positive patients were obtained by retrospective chart review. Positivity with both methods was associated with a diagnosis dermatomyositis with characteristic skin manifestations of varying severity and muscle involvement. Majority of the patients were female (73.7%), mean age of 55.0 (range 12.0-82.0) years at the time of testing. Using the IP as reference, the SAE1 LIA had a sensitivity of 100% (95% CI 82.4-100%), specificity of 99.6% (95% CI 97.7-100%), positive predictive value of 95.0% (95% CI 75.1-99.9%), and negative predictive value of 100% (95% CI 98.5-100%). This study confirms the association of SAE antibodies in patients with dermatomyositis. A combination of IP and the LIA specific for SAE1 may be useful in antibody detection.

Performance Evaluation and Clinical Associations of Immunoassays That Detect Antibodies to Negatively Charged Phospholipids Other Than Cardiolipin.

OBJECTIVES: We evaluate the performance characteristics of antiphosphatidylserine (anti-PS), antiphosphatidylinositol (anti-PI), and antiphospholipid mixture (APhL) enzyme-linked immunosorbent assays (ELISAs) compared with anticardiolipin (aCL) and anti-ß2 glycoprotein I (anti-ß2GPI) in a large group of patients with antiphospholipid (aPL)-related diseases. METHODS: Serum samples from 548 patients from the Hopkins and Jamaican systemic lupus erythematosus cohorts, the PROMISSE cohort, and the Antiphospholipid Standardization Laboratory were examined for immunoglobulin G (IgG)/immunoglobulin M (IgM) positivity in aCL, anti-ß2GPI, anti-PS, anti-PI, and APhL ELISA assays. RESULTS: All IgG assays were associated with one or more thrombotic and/or obstetric manifestations, with an increased risk associated with higher antibody titers. Analytical performance was similar among assays, but IgG assays performed better than IgM counterparts. CONCLUSIONS: Increasing titers of APhL, anti-PS, and anti-PI antibodies could indicate an increased risk of thrombotic and/or obstetric aPL-related manifestations. These assays may be promising biomarkers for particular APS manifestations.

Further comparisons of assays for detecting MAG IgM autoantibodies.

Anti-MAG antibodies are commonly found in the sera of patients with demyelinating sensorimotor neuropathy and IgM paraproteinemia. Our objective here was to compare MAG results obtained by two different laboratories using similar methods (Western blot, EIA, IFA). Western blot (WB) employing MAG from monkey was less sensitive (72.5%) than myelin IFA (92.5%; monkey nerve) and EIA (97.5%; human MAG) when compared to WB using human MAG and is most likely due to methodology (not antigen source). EIA detected low titers of MAG IgM antibodies in suspected patient sera (negative by other methods) that were also SGPG IgM-positive. Patients having low titers by EIA, but negative by WB may have other autoimmune neuropathies without demyelination.

Comparison of immune assays for the detection of anti-HSP70 antibodies in patients with idiopathic sensorineural hearing loss.

BACKGROUND: Detection of anti-heat-shock protein 70 (HSP70) IgG response by Western blot (WB) is of clinical utility in a subset of patients with idiopathic sensorineural hearing loss (SNHL) due to autoimmunity. METHODS: To validate an immune assay for the detection of anti-HSP70 antibody responses in the clinical laboratory, we employed a commercial anti-human HSP70 IgG/A/M ELISA and developed an anti-HSP70 IgG WB test. Using sera from 81 patients with idiopathic SNHL and 100 healthy controls, we assessed each assay performance with results from another diagnostic laboratory that utilizes a WB test. RESULTS: Our results showed a significant lack of agreement between either WB assay and the anti-human HSP70 IgG/A/M ELISA for antibody-positive samples. Comparison of WB assays revealed a significant level of agreement (89.7%) for all samples tested. CONCLUSIONS: Our data suggest that the antigenic targets in WB and ELISA immunoassays differ and demonstrate that the anti-HSP70 IgG WB test is reproducible within and between clinical laboratories. Thus, in the absence of disease-specific markers, the anti-HSP70 IgG WB assay could be of use to detect patients with idiopathic SNHL who might benefit from steroid treatment.

Detection of autoantibodies to 3-hydroxy-3-methylglutaryl-coenzyme a reductase by ELISA in a reference laboratory setting.

BACKGROUND: We investigated the performance of an ELISA for the detection of 3-hydroxy-3-methyl-glutaryl-coenzyme A reductase (HMGCR) IgG antibodies in immune-mediated necrotizing myopathies (IMNM). METHODS: Patients positive for HMGCR antibodies (n=61) or negative (n=78) by protein immunoprecipitation (IP), and healthy controls (n=100) were used to evaluate the ELISA. Unique consecutive serum samples (n=155) received at ARUP Laboratories for HMGCR IgG testing by ELISA were also investigated and analysed for serum muscle enzymes (aldolase, creatine kinase, and myoglobin). The ELISA's sensitivity, specificity, and percentage agreement were assessed relative to IP. Correlation between specific muscle enzyme concentration and the presence of HMGCR antibody was determined. RESULTS: Overall agreement between ELISA and IP was 93.4%. Using the IP as reference, the sensitivity and specificity of the ELISA was 95.1%, and 100%, respectively. Inter- and intra-assay coefficient of variation of the ELISA was <10.0%, and ≤15.0%, respectively. In the consecutive cohort, 21 (13.6%) samples tested positive for HMGCR IgG. Concentrations of aldolase, creatine kinase, and myoglobin were significantly higher (all p<0.0001) in patients positive for HMGCR antibodies at the time of evaluation. CONCLUSIONS: We confirm significant reliability of HMGCR antibodies as measured by the ELISA for the evaluation of IMNM.

Detection of anti-U3-RNP/fibrillarin IgG antibodies by line immunoblot assay has comparable clinical significance to immunoprecipitation testing in systemic sclerosis.

The aim of this study was to evaluate the performance and clinical relevance of a commercially available line immunoblot assay (LIA) for detecting anti-U3-RNP/fibrillarin (anti-U3-RNP), against immunoprecipitation (gold standard). This study involved a multi-ethnic cohort of 1000 American systemic sclerosis (SSc) patients and 50 healthy controls. Antinuclear antibodies and centromere antibodies were detected by indirect immunofluorescent antibody test, anti-topo I by immunodiffusion and anti-RNAP III by ELISA. The presence of anti-U3-RNP in select serum samples was detected by immunoprecipitation (IP) and LIA. By IP, U3-RNP antibody was detected in 75 (7.5 %) patients with SSc. Overall agreement between LIA and IP was very good (κ = 0.966). Analytic sensitivity and specificity of the U3-RNP LIA was 100 and 94.7 %, respectively. Clinical features associated with positivity for the anti-U3-RNP antibody include diffuse cutaneous SSc and increased prevalence of renal crisis, consistent with previous studies that used IP. Testing for U3-RNP antibodies is only performed by a small number of laboratories due to the complexity of both performance and interpretation of the IP. LIA is faster and less complex than IP. Excellent agreement between IP and LIA demonstrates that LIA is an acceptable and attractive alternative to IP for anti-U3-RNP detection.

Ethnic Differences in Autoantibody Diversity and Hierarchy: More Clues from a US Cohort of Patients with Systemic Sclerosis.

OBJECTIVE: To determine the autoantibody repertoire and clinical associations in a multiethnic cohort of American patients with systemic sclerosis (SSc). METHODS: There were 1000 patients with SSc (196 Hispanic, 228 African American, 555 white, and 21 other) who were screened for antinuclear antibodies (ANA), including anticentromere antibodies (ACA) by indirect immunofluorescence assay, antitopoisomerase-1 (topo-1/Scl-70) by immunodiffusion, and anti-RNA polymerase III (RNAP III) by ELISA. Sera from 160 patients with mainly nucleolar and/or speckled ANA pattern, but negative for ACA, Scl-70, and RNAP III, were further characterized by immunoprecipitation for SSc-specific antibodies. RESULTS: The prevalence of antibodies against RNAP III, Th/To, and PM/Scl did not differ significantly among the ethnic groups. The frequency of anti-Scl-70 was lowest in whites (18.0%) compared with 24.0% and 26.8% in Hispanics and African Americans (p = 0.01), respectively. Compared with African American patients, Hispanic and white subjects had a higher frequency of ACA (p < 0.0001) and lower frequency of U3-RNP (p < 0.0001). U3-RNP antibodies were uniquely higher in African American patients, independent of clinical subset, while Th/To autoantibodies were associated with limited cutaneous SSc in white subjects. Overall, Hispanic and African American patients had an earlier age of onset and a predominance of diffuse cutaneous SSc compared with their white counterparts. CONCLUSION: SSc-specific antibodies may predict disease subset; however, the hierarchy of their prevalence differs across ethnic groups. This study provides the most extensive analysis to date on the relevance of autoantibodies in the diagnosis and clinical manifestations of SSc in Hispanic American patients.

Clinical significance and correlations between anti-ß2 glycoprotein I IgA assays in antiphospholipid syndrome and/or systemic lupus erythematosus.

BACKGROUND: The objective of this investigation was to examine the clinical significance of IgA anti-ß2 glycoprotein I (anti-ß2GPI) antibodies and the inter-assay relationships between kits for their determination. METHODS: Serum samples from 269 patients with clinical diagnoses of systemic lupus erythematosus (SLE) and/or antiphospholipid syndrome (APS), individuals positive for antiphospholipid antibodies (aPL) with or without APS or SLE, and 182 controls were tested for anti-ß2GPI IgA antibodies using kits from four manufacturers. RESULTS: The positivity rates for the different IgA anti-ß2GPI antibody kits varied in the disease groups; 7.8-14.7% (SLE only), 12.0-15.7% (SLE and APS/aPL), 14.7-58.8% (APS only), and 17.4-52.2% (aPL only). Kappa agreements between any 2 kits within disease groups were also variable and ranged from 0.25-1.00 (SLE), 0.18-1.00 (SLE and APS/aPL), 0.22-0.94 (APS only), and 0.32-0.91 (aPL only). Univariate analyses also showed variable relative risks for specific APS clinical manifestations with the different kits evaluated. Overall, diagnostic and predictive values for IgA anti-ß2GPI antibodies are kit-dependent; therefore results are not interchangeable. While all 4 kits seem able to predict venous thrombosis tolerably well, there was a variable performance in predicting pregnancy related morbidity. CONCLUSIONS: Efforts to standardize these assays are highly needed prior to their formal adoption in routine clinical evaluation.

Performance Characteristics of Commercial Immunoassays for the Detection of IgG and IgM Antibodies to ß2 Glycoprotein I and an Initial Assessment of Newly Developed Reference Materials for Assay Calibration.

OBJECTIVES: To investigate the performance characteristics and impact of newly developed reference calibrators on the commutability between anti-ß2 glycoprotein I (anti-ß2 GPI) immunoassays in antiphospholipid syndrome (APS) and/or systemic lupus erythematosus (SLE). METHODS: Immunoglobulin G (IgG) and immunoglobulin M (IgM) anti-ß2 GPI immunoassays from four manufacturers were evaluated. Serum samples from 269 patients (APS only, n = 31; SLE and APS, n = 83; SLE only, n = 129; pregnancy-related clinical manifestations without APS, n = 26) and 162 women with histories of successful pregnancies were tested. Results were expressed in kit-specific arbitrary units and in the calibrator reference units (RUs) based on 99th percentile cutoff values. Diagnostic accuracies, correlation between kits, and specific clinical manifestations in APS were investigated. RESULTS: The sensitivities of the assays ranged from 15.8% to 27.2% (IgG) and 12.3% to 15.8% (IgM) while specificities ranged from 79.4% to 86.5% (IgG) and 80.6% to 84.5% (IgM). There was moderate to almost perfect interassay reliability (Cohen κ, 0.69-0.98), and Spearman correlation coefficients were generally improved when results of the IgG determinations were expressed in RUs. CONCLUSIONS: Although qualitative agreements between immunoassays for both antibody isotypes are acceptable, correlations with APS clinical manifestations were kit dependent. Only the use of IgG reference material improved quantitative correlations between assays.

Determination of cytokine responses using a multiplexed fluorescent microsphere immunoassay.

We used a multiplexedfluorescent microsphere immunoassay to develop a sandwich capture assay to assess simultaneously the production of thymus helper (TH) 1- and TH2-type cytokines in tissue culture supernatant obtained from stimulated peripheral blood mononuclear cells. The assay then was used to assess the cytokine production of patients with hyperimmunoglobulinemia E syndrome and in cord blood from neonates. The multiplexed assay has a reportable range of less than 10 to 50,000 pg/mL. For linearity and recovery studies, R2 values for the 6 cytokines ranged from 0.988 to 0.999 for samples spiked with known concentrations of recombinant cytokine standards and for patient samples. The assay showed good specificity, with little cross-reactivity between cytokines. Results from supernatants of Staphylococcus aureus-stimulated peripheral blood mononuclear cells obtainedfrom 6 patients with hyperimmunoglobulinemia E syndrome showed significantly less interferon (IFN)-gamma production than cells from healthy control subjects. Cord blood cells from neonates produced significantly less interleukin 12 and IFN-gamma than cells from adults in group B streptococci-stimulated mononuclear cells. The fluorescent multiplexed microsphere immunoassay can be used to quantitate multiple cytokines from 1 sample and should be useful for further understanding of the cytokine role in disease.

Interpretation of ANA indirect immunofluorescence test outside the darkroom using NOVA view compared to manual microscopy.

OBJECTIVE: To evaluate NOVA View with focus on reading archived images versus microscope based manual interpretation of ANA HEp-2 slides by an experienced, certified medical technologist. METHODS: 369 well defined sera from: 44 rheumatoid arthritis, 50 systemic lupus erythematosus, 35 scleroderma, 19 Sjögren's syndrome, and 10 polymyositis patients as well as 99 healthy controls were examined. In addition, 12 defined sera from the Centers for Disease Control and 100 random patient sera sent to ARUP Laboratories for ANA HEp-2 IIF testing were included. Samples were read using the archived images on NOVA View and compared to results obtained from manual reading. RESULTS: At a 1 : 40/1 : 80 dilution the resulting comparison demonstrated 94.8%/92.9% positive, 97.4%/97.4% negative, and 96.5%/96.2% total agreements between manual IIF and NOVA View archived images. Agreement of identifiable patterns between methods was 97%, with PCNA and mixed patterns undetermined. CONCLUSION: Excellent agreements were obtained between reading archived images on NOVA View and manually on a fluorescent microscope. In addition, workflow benefits were observed which need to be analyzed in future studies.

Anti-NMDA-receptor antibody encephalitis: performance evaluation and laboratory experience with the anti-NMDA-receptor IgG assay.

BACKGROUND: Antibodies targeting the NR1 subunit of the N-methyl-d-aspartate-receptor (NMDAR) are considered diagnostic for a novel form of autoimmune encephalitis. We report the validation of a qualitative indirect immunofluorescence antibody (IFA) test for the detection of anti-NMDAR IgG and describe the attributes of antibody-positive patients. METHODS: The anti-NMDAR IgG assay (Euroimmun Diagnosika, Lübeck, Germany) was validated with serum and cerebrospinal fluid (CSF) specimens from 30 healthy and 50 disease controls as well as 5 anti-NMDAR IgG-positive individuals. Consecutive specimens (n=1671) for anti-NMDAR IgG antibodies were evaluated and positive specimens titrated to end-point [starting dilutions: CSF; 1:1 and serum; 1:10]. In a subset of antibody-positive patients, we sought clinical information for correlation with diagnostic and treatment outcomes. RESULTS: The assay demonstrated excellent performance characteristics in all groups evaluated. Of the 1671 specimens tested, 1389 were unique cases with a positivity rate of 9.0% (n=123). For the antibody-positive samples, the female to male ratio was 2:1 with a prevalence of 46% in the pediatric population (≤17 years). Antibody titers were titrated to end-point for 106/123 specimens [45 CSF, 41 sera, and 20 CSF and serum pairs] with more than 75% having titers greater than 1:10 (CSF) and 1:20 (serum). Overall, high levels of these antibodies showed correlation to disease severity with variable response to treatment in the subset of patients evaluated. CONCLUSION: Our data suggests a high prevalence for anti-NMDAR antibody encephalitis irrespective of age and gender in our unselected disease cohort with support for measuring antibody titers in the evaluation of these patients.

Screening for IgG antinuclear autoantibodies by HEp-2 indirect fluorescent antibody assays and the need for standardization.

We evaluated 5 commercially available HEp-2 antinuclear antibody (ANA) indirect fluorescent antibody (IFA) assays using patient serum samples from 45 patients with rheumatoid arthritis, 50 with systemic lupus erythematosus (SLE), 35 with scleroderma, 20 with Sjögren syndrome, 10 with polymyositis, and 100 healthy control subjects. In addition, 12 defined serum samples from the Centers for Disease Control and Prevention and 100 patient serum samples sent to ARUP Laboratories (Salt Lake City, UT) for ANA IFA testing were also examined (n = 372). Standardization among the HEp-2 IFA assays occurred when they exhibited the same titer ± 1 doubling dilution. Agreement of the 5 assays was 78%. Within the specific groups of serum samples, agreement ranged from 44% in scleroderma serum samples to 93% in healthy control subjects, with 72% agreement in the SLE group. Variations in slide and substrate quality were also noted (ie, clarity, consistency of fluorescence, cell size, number and quality of mitotic cells). Along with subjectivity of interpretation, HEp-2 IFA assays are also vulnerable to standardization issues similar to other methods for ANA screening.