Introduction & Objective: The objective of this study was to determine the sensitivity and specificity of CA 19-9 test in diagnosis of gastric cancer patients.

Materials & Methods: This prospective and cross-sectional study was carried out on 35 patients with gastric cancer and 35 patients without adenocarcinoma of gaster as a control group. Theses patients were referred to alimentary and pathology wards in Ekbatan Hospital of Hamadan city. After selection of the patients who had the inclusion criteria, CA19-9 level was determined, and information collected in a checklist. Then statistical analysis was performed using c²  test.

Results: Cut off point of 35 was determined as a suitable point with high sensitivity and specificity for diagnosis of gastric carcinoma. In cut off point of 35 the sensitivity and specificity was 77.1% and 97.1% respectively. CA 19-9 was a fairly good test for diagnosis of gastric cancer before performing any invasive methods.

Conclusion: CA19-9 is a sensitive and specific test for gastric cancer.