Snyder, Melissa R.

Abstract Background Infliximab (IFX) is a chimeric monoclonal antibody targeting tumor necrosis factor-α, used for the management of autoimmune and inflammatory diseases. Immunogenicity to this protein drug may lead to therapeutic failure. Laboratory testing for serum IFX and antidrug antibodies (ADAs) is available for the evaluation of clinical nonresponsiveness. The purpose of this study was to compare the performance of testing methodologies used by 2 clinical reference laboratories for the quantification of IFX and detection of ADAs. Methods Deidentified serum samples submitted for clinical testing were selected (n = 120) and tested at both sites. A trypsin-based LC-MS/MS assay for IFX and a bridging electrochemiluminescent immunoassay (ECLIA) for ADAs (Mayo Clinic) and a functional cell-based reporter gene assay (RGA) to measure both bioactive drug concentrations and neutralizing ADAs (ARUP Laboratories) were compared. Results In all, 105 samples had measurable concentrations of IFX by both methods and yielded a correlation coefficient (r) = 0.917, slope = 1.028, and intercept = −0.377. One outlier measured <1.0 μg/mL by LC-MS/MS and 37 μg/mL by RGA, which was confirmed to be attributed to the presence of adalimumab. Regarding detection of ADAs, 81 of 120 samples were negative by ECLIA and RGA, whereas 30 of 120 were positive by both methods, resulting in an overall 92.5% agreement. Conclusion Although there are substantial methodological differences in the assays used for detecting IFX and ADAs, results show significant concordance between the clinically validated methodologies performed in different laboratories.

Abstract Background Antinuclear antibody (ANA)5 testing is routinely performed during evaluation of patients with a suspected connective tissue disease (CTD), yet the question of which method is most appropriate remains controversial. The purpose of this study was to evaluate the clinical utility of ANA testing by an enzyme immunoassay (EIA), an immunofluorescence assay (IFA), and a multiplex immunoassay (MIA) in a routine laboratory population. Methods Samples (n = 1000) were collected from specimens submitted for ANA testing by EIA (Bio-Rad). All samples were subsequently analyzed by IFA (Zeus) and MIA (Bio-Rad). The sample cohort was weighted to represent the routine testing population. Diagnostic information was obtained by chart review. Results For the diagnosis of a CTD, ROC curve analysis demonstrated no significant differences between IFA (area under the curve 0.81) and EIA (0.84) (P = 0.25), with overlay of a single point for the MIA. When normalized to a specificity of approximately 90%, the sensitivities of the MIA, EIA, and IFA were 67%, 67%, and 56%, respectively. By varying the clinical cutoff, the IFA could achieve the highest sensitivity of 94%; however, the corresponding specificity was only 43%. In contrast, a strongly positive EIA had a specificity of 97%, although, at this cutoff, the sensitivity was only 40%. Conclusions Although the overall diagnostic performance of the IFA, EIA, and MIA were not statistically different, the clinical sensitivity and specificity varied dramatically based on the positive/negative cutoff. Knowledge about the performance characteristics of each method will significantly aid in the interpretation of ANA testing.

ABSTRACTIntroduction: Multifocal motor neuropathy (MMN) is a motor only, asymmetric onset neuropathy that is relatively treatment‐refractory compared with classic chronic inflammatory demyelinating polyradiculoneuropathy (CIDP) and multifocal acquired demyelinating sensory and motor (MADSAM) neuropathy. Methods: We reviewed 35 patients seropositive for GM1 (monosialo‐asialo [immunoglobulin M, IgM; immunoglobulin G, IgG]) and/or GD1b (disialo [IgG, IgM]) autoantibodies having MMN, classic CIDP, or MADSAM. Immune‐treatment responsiveness and clinical course was compared with antibody negative disease controls. Results: Seventy‐nine percent of seropositives with an initial diagnosis of MMN were immunotherapy responsive compared with 46% of seronegatives (P = 0.045). Eight ganglioside antibody positive MMN patients of 19 (42%) developed sensory findings consistent with MADSAM compared with 3 of 41 (7%) seronegative MMN patients (P = 0.003). MMN and MADSAM patients with ganglioside antibody positivity had more sustained treatment responses (P = 0.03). Discussion: Patients initially diagnosed with MMN seropositive for diverse GM1 autoantibodies appear more likely to have sustained treatment response and evolution to MADSAM. Muscle Nerve 57: 1000–1005, 2018

SummaryBackgroundTissue transglutaminase (tTG) immunoglobulin A (IgA) testing is a sensitive adjunct to the diagnosis of coeliac disease. The threshold for positivity was developed for diagnosis, with negative results reported as below the reference value (<4 U/mL).AimTo investigate if an undetectable (tTG IgA<1.2 U/mL) is more predictive of healing compared to patients with negative but detectable serology (1.2‐3.9 U/mL).MethodsWe performed a retrospective study of 402 treated coeliac disease patients seen at the Mayo Clinic with negative tTG IgA values drawn within 1 month of duodenal biopsy between January 2009 and December 2015. The Corazza‐Villanacci score was used to assess mucosal healing. The presence of gastrointestinal symptoms was also collected. Logistic regression was used to assess the relationship of clinical variables with a normal biopsy.ResultsPatients with undetectable titres more frequently had normal duodenal histology compared to patients with detectable tTG IgA levels (117/240 vs. 53/162; OR=1.96; 1.292, 2.961). Asymptomatic patients more frequently had normal duodenum as compared to symptomatic patients (88/163 vs. 82/239; OR=2.25; CI: 1.494, 3.377). Patients with undetectable serology and on a gluten‐free diet for ≥2 years were more likely to have no villous atrophy compared to patients with detectable serology (148/192 vs. 55/88; OR=2.02; CI: 1.17, 3.49).ConclusionIn subjects recovering from coeliac disease with negative tTG IgA serology, an undetectable titre is associated with normal histology on follow‐up biopsy.

ABSTRACTObjectives:Guidelines for diagnosing celiac disease (CD) recommend initial testing with a highly sensitive serologic test for anti–tissue transglutaminase immunoglobulin A antibodies (tTG IgA). When the probability of CD is high, IgA deficiency should be considered. The 2 approaches to address this include measuring “both tTG IgA and tTG IgG” or measuring “total IgA.” We aim to assess the utility of an isolated positive tTG IgG result in diagnosing CD.Methods:We conducted a retrospective review of patients undergoing serologic testing for CD from January 1997 to June 2014. Patients with positive tTG IgG and negative tTG IgA were included. Moreover, all patients who had any other positive CD‐specific serologic findings were excluded. Demographics, clinical presentation, tests, and biopsy results were recorded.Results:The indication for checking celiac serology was gastrointestinal symptoms in 172 of 233 patients, iron deficiency anemia in 12, and high‐risk screening in 48. Small bowel biopsy was performed in 178 patients (77%); 160 had normal results and 18 had histologic changes suggestive of enteropathy. Nine patients had increased intraepithelial lymphocytes, and 9 had partial villous atrophy. Only 6 cases of CD were, however, confirmed. The utility of isolated tTG IgG in diagnosis of CD was low at 3% (6/178).Conclusion:In this cohort of patients, the utility of isolated tTG IgG in diagnosing CD was low at 3%.

Objective Relapse following remission is common in antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis (AAV), particularly with ANCAs directed at proteinase 3 (PR3). This study was undertaken to evaluate the association of an increase in PR3‐ANCA level with subsequent relapse. Methods Data from the Rituximab versus Cyclophosphamide for ANCA‐Associated Vasculitis (RAVE) trial were used. Starting from the time of achieving complete remission, serial measurements by direct and capture enzyme‐linked immunosorbent assays (ELISAs) were analyzed in 93 patients with PR3‐ANCA, using Cox proportional hazards regression. Results An increase in PR3‐ANCA level was identified in 58 of 93 subjects (62.4%) by direct ELISA and in 59 of 93 (63.4%) by capture ELISA. Relapses occurred in 55 of 93 subjects (59.1%), with 25 and 21 occurring within 1 year after an increase by direct ELISA and capture ELISA, respectively. An increase by direct ELISA was associated with subsequent severe relapses (hazard ratio [HR] 4.57; P < 0.001), particularly in patients presenting with renal involvement (HR 7.94; P < 0.001) and alveolar hemorrhage (HR 24.19; P < 0.001). Both assays identified increased risk for severe relapse in the rituximab group (HR 5.80; P = 0.002 for direct ELISA and HR 4.54; P = 0.007 for capture ELISA) but not the cyclophosphamide/azathioprine group ( P = 0.103 and P = 0.197, respectively). Conclusion The association of an increase in PR3‐ANCA level with the risk of subsequent relapse is partially affected by the PR3‐ANCA detection methodology, disease phenotype, and remission induction treatment. An increase in PR3‐ANCA level during complete remission conveys an increased risk of relapse, particularly severe relapse, among patients with renal involvement or alveolar hemorrhage and those treated with rituximab. Serial measurements of PR3‐ANCA may be informative in this subset of patients, but the risk of relapse must be weighed carefully against the risks associated with therapy.

Growing evidence suggests that pretransplant alpha‐fetoprotein (AFP) predicts outcomes of hepatocellular carcinoma (HCC) patients treated with liver transplantation. We aimed to determine whether pretransplant AFP, Lens culinaris agglutinin‐reactive alpha‐fetoprotein (AFP‐L3), and des‐gamma‐carboxyprothrombin (DCP) predicted HCC recurrence after transplantation. A retrospective cohort study of 313 HCC patients undergoing transplantation between 2000 and 2008 was conducted, and 48 (15.3%) developed recurrence during a median follow‐up of 90.8 months. The 127 patients with available serum drawn before transplantation were included; they included 86 without recurrence and 41 with recurrence. Serum was tested for AFP, AFP‐L3%, and DCP in a blinded fashion with the μTASWako i30 immunoanalyzer. All biomarkers were significantly associated with HCC recurrence. The hazard ratios (HRs) were 3.5 [95% confidence interval (CI), 1.9‐6.7; P < 0.0001] for DCP ≥ 7.5 ng/mL and 2.8 (95% CI, 1.4‐5.4; P = 0.002) for AFP ≥ 250 ng/mL. The HR increased to 5.2 (95% CI, 2.3‐12.0; P < 0.0001) when AFP ≥ 250 ng/mL and DCP ≥7.5 ng/mL were considered together. When they were combined with the Milan criteria, the HR increased from 2.6 (95% CI, 1.4‐4.7; P = 0.003) for outside the Milan criteria to 8.6 (95% CI, 3.0‐24.6; P < 0.0001) for outside the Milan criteria and AFP ≥ 250 ng/mL and to 7.2 (95% CI, 2.8‐18.1; P < 0.0001) for outside the Milan criteria and DCP ≥7.5 ng/mL. Our findings suggest that biomarkers are useful for predicting the risk of HCC recurrence after transplantation. Using both biomarkers and the Milan criteria may be better than using the Milan criteria alone in optimizing the decision of liver transplantation eligibility. Liver Transpl 21:599–606, 2015. © 2015 AASLD.

AbstractBACKGROUNDMeasurement of IgG subclasses is a useful tool for investigation of humoral immune deficiency in the presence of total IgG within reference intervals and IgG4-related disease. Nephelometry has been the method of choice for quantification. We describe an LC-MS/MS method that can multiplex all 4 subclasses along with total IgG by use of either IgG subclass-specific peptide stable isotope–labeled internal standards or a surrogate digest standard for quantification and does not rely on antigen/antibody reactions.METHODSWe combined serum with labeled internal peptide standards and intact purified horse IgG. Samples were denatured, reduced, alkylated, and digested. We analyzed the digested serum by LC-MS/MS for IgG subclasses 1–4 and total IgG.RESULTSWe assayed 112 patient sera by LC-MS/MS and immunonephelometry. The mean of the slopes and R2 values for IgG1, IgG2, IgG3, IgG4, and IgG were 1.18 and 0.93, respectively. Interassay imprecision for the LC-MS/MS method was &lt;15% for total IgG and subclasses and was slightly improved by use of a calibrator peptide from an exogenous horse IgG. Summed total IgG correlated with the measured total IgG within 10%. Reference intervals and analytical measuring range were all similar to our previous validation data for the immunonephelometry assays.CONCLUSIONSTotal IgG and IgG subclasses 1, 2, 3, and 4 can be quantified by LC-MS/MS with performance comparable to nephelometry.