Validation of methods to assess potential biomarkers in pediatric patients with esophageal eosinophilia

摘要

AIM:To validate methods for determining mast cell density,extracellular major basic protein content,and presence of fibrosis in esophageal eosinophilia.METHODS:Twenty specimens with > 20 eosinophils/high-power field(hpf) classified as high eosinophil density(HE) and 20 specimens with < 5 eosinophils/hpf classified as low esophageal density(LE) were identified.All 40 specimens underwent immunohistochemical staining and trichrome staining.Mast cell density,extracellular major basic protein(MBP) density,and presence of subepithelial fibrosis were assessed in a standardized manner.All specimens were evaluated by two separate observers and by a single observer on two separate occasions to evaluate reproducibility of the methods.RESULTS:A strong inter-observer correlation was noted for both peak and mean mast cell counts(r = 0.725,P < 0.0001 and r = 0.823,P < 0.0001).A strong intraobserver correlation also was noted for both peak and mean mast cell counts(r = 0.752,P < 0.0001 and r =0.878,P < 0.0001).A very strong inter-observer correlation was noted for both peak(τ = 0.867,P < 0.0001)and mean extracellular MBP densities(r = 0.925,P <0.0001).A very strong intra-observer correlation was noted for both peak(τ = 0.875;P < 0.0001) and mean extracellular MBP densities(r = 0.956,P < 0.0001).Excellent inter-rater reliability was found for fibrosis(κ= 0.887).Mast cell and MBP densities,as well as presence of fibrosis,were significantly increased in HE vs LE.The HE group had significantly higher intraepithelial mast cell peak(29.35 ± 21.61 vs 12.45 ± 8.26,P =0.002) and mean(19.84 ± 15.81 vs 6.35 ± 4.5,P =0.001) densities than the LE group.The HE group had significantly higher peak extracellular MBP(2.35 ± 0.67vs 0.45 ± 0.61,P < 0.001) and mean extracellular MBP(1.95 ± 0.76 vs 0.20 ± 0.29,P < 0.0001) densities than the LE group.Seventy-three percent of patients with HE(11/15) had fibrosis,whereas only 10% of patients with LE(1/10) had fibrosis(P < 0.01).MBP performed the best in predicting classification of HE vs LE,with mean MBP demonstrating 100% sensitivity and95% specificity at the optimal cut point.CONCLUSION:This study provides methodology and proof-of-concept for future evaluation of these biomarkers for differentiating esophageal eosinophilic diseases such as reflux esophagitis and eosinophilic esophagitis.