1.6 Laboratory test Hb concentration will be determined by the cyanmethemoglobin method, serum ferritin will be determined by a radio immunometric assay. Serum transferrin receptor will be measured by enzyme-linked immunosorbent assay (ELISA). Stool will be tested for the presence of occult blood by the guaiac reaction (Occultotest, Ames Co.,Elkhart, Inc.,. USA). Serum pepsinogen and gastrin will be measured by radioimmunoassay.