Table 1.

Main studies reporting the prevalence of anaemia in adult patients with autoimmune atrophic gastritis (AAG).

Authors	Year	Setting	Patients (n)	Enrolled at AAG Diagnosis	Mean Age (years)	Overall Anaemia (%)	PA (%)	IDA (%)	Major Findings
Burman et al. [11]	1991	Internal medicine	86	Yes	56	80.2	80.2	NA	High PCA levels associated with PA
Hersko et al. [6]	2006	Haematology	160	NS	59	75.0	18.1	51.8	Microcytic anaemia more common in younger age
Lahner et al. [12]	2009	Gastroenterology	165	Yes	54	94.5	49.0	45.5	PCA and anti-intrinsic factor antibodies yield 73% accuracy PA diagnosis
Miceli et al. [4]	2012	Gastroenterology	99	Yes	58	59.6	59.6	0	PA was the most common cause of AAG diagnosis
Lahner et al. [13]	2015	Gastroenterology	83	Yes	59	51.8	51.8	NA	A genetic variant of transcobalamin 2 was related to PA
Zhang et al. [14]	2017	Gastroenterology	275	Yes	61	19.3	5.4	8.4	No clear gender differences; microcytic anaemia more common in younger age
Kalkan et al. [15]	2017	Gastroenterology	355	NS	57	30.1	30.1	NA	PA more common in older patients
Carabotti et al. [16]	2017	Gastroenterology	379	Yes	55	88.4	53.6	34.8	PA more frequent in patients without gastrointestinal symptoms
Villanacci et al. [17]	2017	Pathology	138	NS	48	54.7	25.0	29.7	IDA more common than PA
Lenti et al. [18]	2019	Gastroenterology	291	Yes	60	49.5	23.4	11.7	Isolated MCV alterations associated with greater AAG diagnostic delay

Abbreviations: IDA, iron deficiency anaemia; MCV, mean corpuscular volume; NA, not assessed; NS, not specified; PA, pernicious anaemia; PCA, anti-parietal cell antibody. Studies exploring atrophic gastritis prior to H. pylori discovery were not included. Mean age refers to anaemic patients only, whenever this datum is available.