Clinical evaluation of the BioPlex 2200 Celiac IgA and IgG Kits — A novel multiplex screen incorporating an integral check for IgA deficiency

Abstract

IntroductionCeliac disease screening is commonly based on detection of IgA anti-tissue transglutaminase (TTGA). IgA deficiency (IgAD) is associated with celiac disease and must be identified to enable use of IgG based assays in these patients. The BioPlex® 2200 Celiac IgA and IgG kits use Luminex methodology to provide a method of simultaneously measuring TTG and deamidated gliadin peptide (DGP) antibody levels using a fully automated random access analyzer based on Luminex® technology. Separate kits are available for IgA (TTGA and DGPA) and IgG (TTGG and DGPG) isotypes. The IgA based kit includes a novel “IgA Verification Bead” (AVB) to check for IgAD (at <0.07g/L) to ensure that these patients are identified and tested using the IgG based kit. AimTo perform a clinical and technical evaluation of the BioPlex® 2200 Celiac IgA and IgG kits. Methods116 sera from 116 biopsy proven celiac disease patients were tested (58 new presentations on a gluten containing diet and 58 known TTGA positive patients on a gluten free diet but with suspected poor compliance). IgAD was present in 5 patients. Ability to flag IgAD sera was assessed by analysis of 29 IgAD and 200 non-IgAD sera. Specificity was calculated from 124 unselected consecutive disease control sera. ResultsSensitivity and specificity for IgAD were 100%. Screening with TTGA and adding TTGG when IgAD was identified, gave clinical sensitivity of 100% for celiac disease. Specificity was 100% for TTGA and TTGG, and 98% and 97% for DGPA and DGPG respectively. ConclusionUse of the BioPlex® 2200 Celiac IgA and Celiac IgG kits in a standard protocol gave excellent sensitivity and specificity with highly effective detection of IgAD, no false positive IgAD flags and little evidence of interference from high IgA levels. The ability to detect IgAD without pre-screening with a separate IgA assay should have a significant beneficial impact on laboratory workflow by identifying those patients requiring IgG based testing and IgA measurement to confirm IgAD.