Cow's milk allergy is one of the most common food allergies among younger children. We investigated IgE antibodies to milk, and IgE and IgG4 antibodies to casein, α-lactalbumin and β-lactoglobulin in cow's milk allergic (CMA) and non-allergic (non-CMA) children in order to study their clinical usefulness. Eighty-three children with suspected milk allergy (median age: 3.5 years, range: 0.8-15.8 years) were diagnosed as CMA (n = 61) or non-CMA (n = 22) based on an open milk challenge or convincing clinical history. Their serum concentrations of allergen-specific (s) IgE and IgG4 antibodies were measured using ImmunoCAP®. For the sIgG4 analysis, 28 atopic and 31 non-atopic control children were additionally included (all non-milk sensitized). The CMA group had significantly higher levels of milk-, casein- and β-lactoglobulin-sIgE antibodies as compared to the non-CMA group. The casein test showed the best discriminating performance with a clinical decision point of 6.6 kUA/L corresponding to 100% specificity. All but one of the CMA children aged > 5 years had casein-sIgE levels > 6.6 kUA/L. The non-CMA group had significantly higher sIgG4 levels against all three milk allergens compared to the CMA group. This was most pronounced for casein-sIgG4 in non-CMA children without history of previous milk allergy. These children had significantly higher casein-sIgG4 levels compared to any other group, including the non-milk sensitized control children. High levels of casein-sIgE antibodies are strongly associated with milk allergy in children and might be associated with prolonged allergy. Elevated casein-sIgG4 levels in milk-sensitized individuals on normal diet indicate a modified Th2 response. However, the protective role of IgG4 antibodies in milk allergy is unclear.

IgG anti-integrin αvβ6 autoantibodies (IgG anti-αvβ6) have been described as highly sensitive and specific markers of ulcerative colitis (UC) in the sera of Japanese inflammatory bowel disease (IBD) patients. We aimed to evaluate the diagnostic performance of IgG anti-αvβ6 as a biomarker in Swedish patients with IBD or irritable bowel syndrome (IBS). The study included adult UC (n = 59), Crohn’s disease (CD, n = 38), and IBS patients (n = 100). Partial Mayo score and Harvey–Bradshaw index were used to assess disease severity for UC and CD, respectively. Serum levels of IgG anti-αvβ6, reported as absorbance units (AU), were measured using an in-house ELISA where the 95th percentile of 76 healthy controls defined positivity. Faecal calprotectin (fCP) was measured using a commercial assay. The majority of the IBD patients were on medical treatment, and many were in remission (UC: 40.7%; CD: 47.4%). Seventy-one percent of the UC patients, 74.2% of CD patients, and 23.1% of the IBS patients had fCP test results >50 mg/kg. The UC group had significantly higher IgG anti-αvβ6 levels (median: 1.76 AU) than the CD and IBS groups (0.34 and 0.31 AU, both p < 0.0001). The diagnostic sensitivity of IgG anti-αvβ6 in UC was 76.3%, and the specificities were 79.0% (vs. CD) and 96.0% (vs. IBS). The IgG anti-αvβ6 levels related to disease severity of the UC patients (p < 0.01–0.05). Our study shows that IgG anti-αvβ6 is associated with UC in Swedish IBD patients and that the levels of the autoantibodies reflect disease severity. IgG anti-αvβ6 could be an attractive complement to fCP in the diagnostic work up of IBD patients.

Background and Aims: The diagnostic and prognostic properties of anti-integrin αvβ6 immunoglobulin G (IgG) autoantibodies in ulcerative colitis (UC) are poorly understood. We aimed to assess the diagnostic performance of anti-integrin αvβ6 autoantibodies and examine their association with disease outcomes. Methods: Serum samples from a Swedish inception cohort of patients with suspected inflammatory bowel disease (IBD, n = 473) were analyzed using an in-house fluorescence enzyme immunoassay based on EliA technology. Findings were validated in a Norwegian population-based inception cohort (n = 570). Diagnostic performance was assessed by calculating the area under the curve (AUC) with 95% confidence intervals and determining sensitivity and specificity. Reclassification was evaluated using the net reclassification index. Results: In the discovery cohort, patients with UC, IBD-unclassified, or colonic Crohn’s disease exhibited higher median autoantibody levels compared to symptomatic and healthy controls. In the validation cohort, the autoantibody demonstrated 79% sensitivity and 94% specificity for UC vs symptomatic controls at a cut-off of 400 UA/l. Its diagnostic performance (AUC = 0.92, 95% CI, 0.89-0.95) was superior to hs-CRP (AUC = 0.65, 95% CI, 0.60-0.70, P < .001) and faecal calprotectin (fcalpro) (AUC = 0.88, 95% CI, 0.84-0.92, P = .09). Combining the autoantibody with fcalpro further improved diagnostic accuracy (AUC = 0.97, 95% CI, 0.95-0.98) and patient reclassification (P < .001). Autoantibody positivity was associated with a severe phenotype of UC, characterised by increased inflammatory activity and higher IL-17A and granzyme B levels. Higher autoantibody levels were linked to an aggressive disease course, remaining stable in aggressive UC but decreasing in indolent disease (P = .003). Conclusions: Anti-integrin αvβ6 is a reliable diagnostic and prognostic marker for UC, with potential clinical implementation.

Background: Eosinophilic cationic protein (ECP) is associated with airway inflammation and asthma. However, the clinical value of measuring ECP in childhood asthma is not fully known. We aimed to study the diagnostic performance of serum ECP and other common asthma biomarkers, individually and in combinations. Methods: In a cross-sectional study, 5–16-year-old children with current asthma (CA) (n = 37), transient asthma (TA) (n = 43), (previous history of wheezing/asthma), and healthy children (HC) (n = 86) were investigated for ECP, blood eosinophil count (B-Eos), fractional exhaled nitric oxide (FeNO), and lung function, i.e., spirometry (forced expiratory volume during the first second [FEV1]/forced vital capacity [FVC] ratio). Results: Both ECP and B-Eos were higher in CA compared to TA (p < 0.01) and HC (p < 0.0001). ECP and B-Eos were also higher in TA compared to HC (p < 0.05 and p < 0.001, respectively). FeNO was higher in CA (p < 0.0001) and TA (p < 0.01) compared to HC but similar between the asthma groups. The FEV1/FVC ratio was lower in CA compared to TA and HC (both p < 0.01) but similar between TA and HC. The best diagnostic performance regarding CA was found for ECP and B-Eos with receiver operating characteristics area under curve (AUC) of 0.801 and 0.810, respectively. The optimal cutoff for ECP (29 μg/L) yielded a sensitivity and specificity of 70.3% and 81.4%. The corresponding AUCs for FeNO and FEV1/FVC were 0.732 and 0.670, respectively. ECP and B-Eos showed the highest AUCs (0.669 and 0.673) for differentiation between CA and TA. Combining ECP with FeNO and FEV1/FVC increased the odds ratio (OR) for having CA from OR 3.97–10.3 for the single biomarkers to OR 20.2 (95% confidence interval: 5.76–68.6). Conclusion: Our results show that serum ECP is a reliable biomarker in the diagnosis of childhood asthma, with additional value in combination with FeNO and FEV1/FVC, and that ECP can be an alternative to B-Eos.