Michael P. Horn

Anti-neutrophil cytoplasmic antibodies (ANCA) directed to proteinase 3 (PR3) represent highly established markers for patients with ANCA-associated vasculitis (AAV). PR3-ANCA have also demonstrated utility in the management of inflammatory bowel disease (IBD). More specifically, PR3-ANCA discriminate individuals with ulcerative colitis (UC) from Crohn’s disease (CD) patients and are associated with disease severity, activity, and treatment non-response. Here, we aim to summarize the current data on the diagnostic utility of PR3-ANCA in IBD. A structured, systematic literature review, including three electronic databases, was conducted on June 6th, 2023, to identify studies assessing the diagnostic accuracy of the QUANTA Flash^® PR3 assay in UC vs. CD patients. Electronic searches were supplemented by hand searching. A hierarchical, bivariate, mixed-effect meta-analysis was conducted using the metandi function, as per the Cochrane collaboration recommendations. Study quality was assessed using the QUADAS-2 tool, which considers the risk of bias and applicability. Six out of a hundred and eleven citations met the inclusion criteria and reported QUANTA Flash^® PR3 diagnostic accuracy in UC vs. CD (UC, n = 667, CD, n = 682 patients). The sensitivity/specificity point estimate for UC was 34.9%/95.9%. This resulted in a Diagnostic Odds Ratio (DOR) of 12.6. The risk of bias was low in the index test and reference standard domains. Four of the six studies (67%) showed an unclear risk of bias in patient selection and in flow and timing domains. All studies had low concerns about applicability in all the domains. PR3-ANCA measured with the QUANTA Flash^® PR3 assay represent novel diagnostic markers in IBD and enables discrimination between UC and CD.

Antibody testing in inflammatory bowel disease (IBD) can add to diagnostic accuracy of the main subtypes Crohn’s disease (CD) and ulcerative colitis (UC). Whether modern modeling techniques such as supervised and unsupervised machine learning are of value for finer distinction of subtypes such as IBD-unclassified (IBD-U) is not known. We determined the antibody profile of 100 adult IBD patients from the Swiss IBD cohort study with known subtype (50 CD, 50 UC) as well as of 76 IBD-U patients. We included ASCA IgG and IgA, p-ANCA, MPO- and PR3-ANCA, and xANCA measurements for computing different antibody panels as well as machine learning models. The AUC of an optimized antibody panel was 85% (95%CI, 78–92%) to distinguish CD from UC patients. The antibody profile of IBD-U patients was closely related to UC. No specific antibody profile was predictive for IBD-U nor for re-classification. The panel diagnostic was in favor of UC reclassification prediction with a correct assignment rate of 69.2–73.1% depending on the cut-off applied. Supervised machine learning could not distinguish between CD, UC, and IBD-U. More so, unsupervised machine learning suggested only two distinct clusters as a likely number of IBD subtypes. Antibodies in IBD are supportive in confirming clinical determined subtypes CD and UC but have limited capacity to predict IBD-U and reclassification during follow-up. In terms of antibody profiles, IBD-U is not a distinct subtype of IBD.

Zusammenfassung. Beim Management von COVID-19 stehen der praktischen Ärztin und dem praktischen Arzt eine Vielzahl von Labortests zur Verfügung. Die Auswahl ist schwierig, gerade weil ein Teil dieser Labortests in der Laienpresse kontrovers diskutiert wird. Im vorliegen-den Artikel diskutieren wir die wichtigen klinischen Fragen und den Beitrag von Labor-tests zur Beantwortung dieser Fragen. Wir beschreiben die häufigsten Testprinzipien und diskutieren deren diagnostischen Wert. Damit bieten wir den praktisch tätigen Ärztinnen und Ärzten eine einfache Übersicht für die klinische Praxis.

Although mRNA-based vaccines against SARS-CoV-2 induce a robust immune response and prevent infections and hospitalizations, there are limited data on the antibody response in individuals with humoral immunodeficiency. The aim of this study was to evaluate the humoral immune response after two vaccine doses with BNT162b2 or mRNA-1273 in patients with humoral immunodeficiency disease. This cross-sectional study assessed 39 individuals with hypogammaglobulinemia under immunoglobulin replacement therapy. IgG anti-SARS-CoV-2 spike protein antibodies (anti-S) were measured 4 weeks to 4 months after two doses of an mRNA vaccine against SARS-CoV-2. The proportion of patients, who developed a humoral immune response to the spike protein were evaluated and compared to 19 healthy controls. After vaccination with two vaccine doses, 26/39 patients (66.7%) with humoral immunodeficiency disease and all healthy controls developed anti-S. In subjects with baseline IgG <3 g/l, only 1/5 (20%) showed a humoral immune response. 10 out of 26 with CVID (38.5%) and 7/9 under immunosuppressive drugs (77.8%) developed no immune response (13 subjects with no response) compared to 0/19 in healthy controls. Subgroup analysis in patients without immunosuppressive drugs revealed lower anti-S in patients with moderate to severe humoral immunodeficiency disease: baseline IgG 5 g/l: 151.5 AU/ml (95%CI 109.0–400.0), healthy controls 250.0 AU/ml (95%CI 209.0–358.0), p = 0.007. In most patients with mild to moderate humoral immunodeficiency we found only slightly lower anti-S antibodies compared with healthy controls after two vaccine doses with BNT162b2 and mRNA-1273. However, in patients with a decreased baseline IgG below 3 g/l and/or under immunosuppressive drugs, we found severely impaired humoral immune responses.

Background The majority of patients with B-cell-depleting therapies show compromised vaccination-induced immune responses. Herein, we report on the trajectories of anti-SARS-CoV-2 immune responses in patients of the RituxiVac study compared with healthy volunteers and investigate the immunogenicity of a third vaccination in previously humoral non-responding patients. Methods We investigated the humoral and cell-mediated immune response after SARS-CoV-2 messanger RNA vaccination in patients with a history with anti-CD20 therapies. Coprimary outcomes were antispike and SARS-CoV-2-stimulated interferon-γ concentrations in vaccine responders 4.3 months (median; IQR: 3.6–4.8 months) after first evaluation, and humoral and cell-mediated immunity (CMI) after a third vaccine dose in previous humoral non-responders. Immunity decay rates were compared using analysis of covariance in linear regression. Results 5.6 months (IQR: 5.1–6.7) after the second vaccination, we detected antispike IgG in 88% (29/33) and CMI in 44% (14/32) of patients with a humoral response after two-dose vaccination compared with 92% (24/26) healthy volunteers with antispike IgG and 69% (11/16) with CMI 6.8 months after the second vaccination (IQR: 6.0–7.1). Decay rates of antibody concentrations were comparable between patients and controls (p=0.70). In two-dose non-responders, a third SARS-CoV-2 vaccine elicited humoral responses in 19% (6/32) and CMI in 32% (10/31) participants. Conclusion This study reveals comparable immunity decay rates between patients with anti-CD20 treatments and healthy volunteers, but inefficient humoral or CMI after a third SARS-CoV-2 vaccine in most two-dose humoral non-responders calling for individually tailored vaccination strategies in this population. Trial registration number NCT04877496; ClinicalTrials.gov number.

There is an increasing body of evidence describing an association between anti Kelch-like protein 11 (KLHL11) encephalitis and various tumors such as seminoma. However, when the diagnosis of neoplasia is uncertain and the clinical syndrome resembles those caused by other etiologies, the possibility of anti-KLHL11 encephalitis may not be obvious during early clinical evaluations. We present the case of a 68-year-old man with clinical features of anti-KLHL11 encephalitis, in whom no clear signs of an active neoplasia could be found. However, a burnt-out germ-cell tumor was suspected. This case highlights the importance of having a high clinical suspicion for anti-KLHL11 encephalitis in patients who exhibit symptoms and signs, even in absence of an active tumor.

Background Immune responses on SARS-CoV-2 vaccination in patients receiving anti-CD20 therapies are impaired but vary considerably. We conducted a systematic review and meta-analysis of the literature on SARS-CoV-2 vaccine induced humoral and cell-mediated immune response in patients previously treated with anti-CD20 antibodies. Methods We searched PubMed, Embase, Medrxiv and SSRN using variations of search terms ‘anti-CD20’, ‘vaccine’ and ‘COVID’ and included original studies up to 21 August 2021. We excluded studies with missing data on humoral or cell-mediated immune response, unspecified methodology of response testing, unspecified timeframes between vaccination and blood sampling or low number of participants (≤3). We excluded individual patients with prior COVID-19 or incomplete vaccine courses. Primary endpoints were humoral and cell-mediated immune response rates. Subgroup analyses included time since anti-CD20 therapy, B cell depletion and indication for anti-CD20 therapy. We used random-effects models of proportions. Findings Ninety studies were assessed. Inclusion criteria were met by 23 studies comprising 1342 patients. Overall rate of humoral response was 0.40 (95% CI 0.35 to 0.47). Overall rate of cell-mediated immune responses was 0.71 (95% CI 0.57 to 0.87). A time interval >6 months since last anti-CD20 therapy was associated with higher humoral response rates with 0.63 (95% CI 0.53 to 0.72) versus Interpretation Patients on anti-CD20 therapies can develop humoral and cell-mediated immune responses after SARS-CoV-2 vaccination, but subgroups such as kidney transplant recipients or those with very recent therapy and depleted B cell are at high risk for non-seroconversion and should be individually assessed for personalised SARS-CoV-2 vaccination strategies. Potential limitations are small patient numbers and heterogeneity of studies included. Funding This study was funded by Bern University Hospital.

Background: Serological tests are a powerful tool in the monitoring of infectious diseases and the detection of host immunity. However, manufacturers often provide diagnostic accuracy data generated through biased studies, and the performance in clinical practice is essentially unclear.Objectives: We aimed to determine the diagnostic accuracy of various serological testing strategies for (a) identification of patients with previous coronavirus disease‐2019 (COVID‐19) and (b) prediction of neutralizing antibodies against SARS‐CoV‐2 in real‐life clinical settings.Methods: We prospectively included 2573 consecutive health‐care workers and 1085 inpatients with suspected or possible previous COVID‐19 at a Swiss University Hospital. Various serological immunoassays based on different analytical techniques (enzyme‐linked immunosorbent assays, ELISA; chemiluminescence immunoassay, CLIA; electrochemiluminescence immunoassay, ECLIA; and lateral flow immunoassay, LFI), epitopes of SARS‐CoV‐2 (nucleocapsid, N; receptor‐binding domain, RBD; extended RBD, RBD+; S1 or S2 domain of the spike [S] protein, S1/S2), and antibody subtypes (IgG, pan‐Ig) were conducted. A positive real‐time PCR test from a nasopharyngeal swab was defined as previous COVID‐19. Neutralization assays with live SARS‐CoV‐2 were performed in a subgroup of patients to assess neutralization activity (n = 201).Results: The sensitivity to detect patients with previous COVID‐19 was ≥85% in anti‐N ECLIA (86.8%) and anti‐S1 ELISA (86.2%). Sensitivity was 84.7% in anti‐S1/S2 CLIA, 84.0% in anti‐RBD+LFI, 81.0% in anti‐N CLIA, 79.2% in anti‐RBD ELISA, and 65.6% in anti‐N ELISA. The specificity was 98.4% in anti‐N ECLIA, 98.3% in anti‐N CLIA, 98.2% in anti‐S1 ELISA, 97.7% in anti‐N ELISA, 97.6% in anti‐S1/S2 CLIA, 97.2% in anti‐RBD ELISA, and 96.1% in anti‐RBD+LFI.The sensitivity to detect neutralizing antibodies was ≥85% in anti‐S1 ELISA (92.7%), anti‐N ECLIA (91.7%), anti‐S1/S2 CLIA (90.3%), anti‐RBD+LFI (87.9%), and anti‐RBD ELISA (85.8%). Sensitivity was 84.1% in anti‐N CLIA and 66.2% in anti‐N ELISA. The specificity was ≥97% in anti‐N CLIA (100%), anti‐S1/S2 CLIA (97.7%), and anti‐RBD+LFI (97.9%). Specificity was 95.9% in anti‐RBD ELISA, 93.0% in anti‐N ECLIA, 92% in anti‐S1 ELISA, and 65.3% in anti‐N ELISA. Diagnostic accuracy measures were consistent among subgroups.Conclusions: The diagnostic accuracy of serological tests for SARS‐CoV‐2 antibodies varied remarkably in clinical practice, and the sensitivity to identify patients with previous COVID‐19 deviated substantially from the manufacturer's specifications. The data presented here should be considered when using such tests to estimate the infection burden within a specific population and determine the likelihood of protection against re‐infection.