All diagnostic patient sera were tested with QUANTA Flash h-tTG IgA from Inova Diagnostics (San Diego, USA) and with EliA Celikey IgA from Thermo Fisher Scientific (Uppsala, Sweden). The latter analyses were performed in batch on stored serum samples (-18°C).
QUANTA Flash h-tTG IgA analyses were performed on the BIO-FLASH (Inova Diagnostics, San Diego, USA) fully automated chemiluminescent immunoassay (CLIA) analyzer. In this assay, purified recombinant human tTG (QUANTA Flash h-tTG IgA) coated on paramagnetic beads is used as antigen and will react with antibodies from the patient's serum sample. The optical system of the analyzer measures the light induced by the antigen-antibody reaction in relative light units (RLU) and, after conversion, expresses results as chemiluminescent units (CU). The cut-off set by Inova Diagnostics for IgA anti-h-tTG antibody positivity is 20 CU.
The Phadia 250 analyzer (Thermo Fisher Scientific, Uppsala) was used to perform the EliA Celikey IgA assays. Phadia 250 is an automated fluorescence enzyme immunoassay (FEIA) analyzer. Human recombinant tissue transglutaminase is used as antigen in this assay.
According to the manufacturer's instructions, the cut-off value of the EliA Celikey IgA assay is 7 U/mL. Test result specific likelihood ratios were calculated using the Bézier method as described in Bossuyt et al. (26) (link).
QUANTA Flash h-tTG IgA analyses were performed on the BIO-FLASH (Inova Diagnostics, San Diego, USA) fully automated chemiluminescent immunoassay (CLIA) analyzer. In this assay, purified recombinant human tTG (QUANTA Flash h-tTG IgA) coated on paramagnetic beads is used as antigen and will react with antibodies from the patient's serum sample. The optical system of the analyzer measures the light induced by the antigen-antibody reaction in relative light units (RLU) and, after conversion, expresses results as chemiluminescent units (CU). The cut-off set by Inova Diagnostics for IgA anti-h-tTG antibody positivity is 20 CU.
The Phadia 250 analyzer (Thermo Fisher Scientific, Uppsala) was used to perform the EliA Celikey IgA assays. Phadia 250 is an automated fluorescence enzyme immunoassay (FEIA) analyzer. Human recombinant tissue transglutaminase is used as antigen in this assay.
According to the manufacturer's instructions, the cut-off value of the EliA Celikey IgA assay is 7 U/mL. Test result specific likelihood ratios were calculated using the Bézier method as described in Bossuyt et al. (26) (link).