Disease entity	Serum IgA antibodies a,b	Serum IgG antibodies
	1. Tissue transglutaminase 2 (anti-TG2 IgA)	1. Tissue transglutaminase 2 (anti-TG2-IgG)c
	2. Anti-endomysium (EMA IgA)	2. Anti-endomysium (EMA IgG)
	3. Deamidated antigliadin (anti-DGP IgA)	3. Deamidated antigliadin (anti-DGP IgG)
	4. Conventional antigliadin (AGA)d	4. Conventional antigliadin (AGA)d
Celiac disease (classic, oligo- and/or monosymptomatic)	95–100 %	90–97 %
Silent celiac disease	90 %	90 %
Latent celiac disease	Borderline – negative	30–60 %
Food allergy	(Borderline) – negative	Partially detectable 15 %–40 %
Irritable bowel	(Borderline) – negative	Partially detectable 30 %–36 %
Normal population	Negativ	25%–30%

^a IgA diagnosis is only sensitive in IgA immunocompetent individuals. Therefore, determining serum IgA levels is necessary to exclude IgA deficiency or identify low IgA values (total IgA < 20 mg/dl).

^b IgA diagnosis is superior to IgG diagnosis in IgA immunocompetent individuals. IgG-based diagnosis should only be used in the case of IgA deficiency (total IgA < 20 mg/dl).

^c Primary diagnosis for the serological detection of celiac disease should be performed according to the sequence of antibody tests given here, starting with anti-TG2 IgA antibodies (anti-TG2-IgG in the case of IgA deficiency). Determining EMA or DGP complements the reliability of TG detection only when this latter is positive.

^d Conventional AGA should no longer be used today, since deamidated gliadin peptides (DGP-IgG antibodies) are significantly more sensitive in the <2-year age group. In the presence of other gastrointestinal diseases, intestinal barrier disorder or following infection, conventional AGA are often nonspecifically elevated and can cause problems in terms of differential diagnosis (e. g. irritable bowel syndrome, food allergy, chronic inflammatory bowel disease) [36].

AGA, anti-gliadin antibodies; DGP, deaminated gliadin peptides; EMA, endomysium antibodies; Ig, immunoglobulin; TG, transglutaminase