The impact of biopsy number and site on the accuracy of intestinal metaplasia detection in the stomach A morphometric study based on virtual biopsies.

Background. Intestinal metaplasia is a risk factor for gastric carcinoma. So far few studies have focused on the efficacy of endoscopic biopsies in detecting intestinal metaplasia in relation with the site and number of biopsies performed. The present study is aimed to assess the efficacy of single and multiple gastric biopsies in the detection and staging of intestinal metaplasia. Material and methods. The studywas conducted on 455 gastrectomies.We defined the extent of intestinal metaplasia on surgical specimens sampled by the “Swiss roll” technique and assessed the efficiency of an increasing number of “virtual” biopsies performed on the same rolls in recognising the true extent of intestinal metaplasia in the antro-angular region. Results. Seventy-four out of 455 cases showed intestinal metaplasia in more than 5% of the antro-angular mucosa. The correlation between antro-angular intestinal metaplasia on rolls and on virtual biopsies was always highly significant, both when a single biopsy was considered and when groups of multiple biopsies (from 2 to 6 samples) were taken into account (p≤0.0001 and rho ranging from 0.304 to 0.817). By increasing the number of biopsies (from 1 to 6) we observed an increase in the rate of correct estimations when 20% extent was used as a cut-off: the increase was statistically significant in both intestinal metaplasia ≥20% and intestinal metaplasia <20% groups (p < 0.0001). The highest value of concordance between intestinal metaplasia extent in virtual biopsies and in rolls was recorded for a set of 4 antral + 1 angular biopsies whereas a set of 2 antral + 1 angular biopsies turned out to be the most effective in terms of number/efficacy. Conclusions. A three biopsy set (2 antral + 1 angular) allows correct detection of intestinal metaplasia extent in 90% of cases.