Table 1: The OLGA staging system. Stage is scored in following way: 1) Scoring atrophy at each single antral/angular biopsy level (row) and corpus biopsy level (column); 2) Calculating mean of degree of atrophy in antral/angular level (A) and corpus level (C); 3) The final prevalence of atrophy at each compartment is calculated and scored on a four-tiered scale (no atrophy = 0%: score = 0, mild atrophy = 1-30%: score = 1, moderate atrophy = 31-60%: score = 2, severe atrophy => 60%: score = 3) [7].

C0 C1 C2 C3
A0 Stage 0 Stage I Stage II Stage III
A1 Stage I Stage I Stage II Stage III
A2 Stage II Stage II Stage II Stage IV
A3 Stage III Stage III Stage IV Stage IV