Diagnostic of Helicobacter Pylori Infection Using Serum Anti-H. Pylori IgG Test

Serologic test the diagnosis of Helicobacter(H.) pylori infection si one of noninvasive test that do not require endoscopy. This study was performed to evaluate the diagnostic value of serum anti-H. pylori lgG test, especially compared with other invasive tests.

From December 1995 to December 1996, one hundred and fifty one patients had UGI endoscopy and serum anti-H. pylori lgG test. They were 48 duodenal ulcer patients(36 active stage and 12 scar stage), 5 duodenitis patients, 19 gastric ulcer patients 2 duodenal ulcer with gastric ulcer patients, 48 gastritis patients, 13 gastric cancer patients, 4 postgastrectomy patients and 12 endoscopically normal patients. Serum anti-H. pylori lgG was measured by enzyme immunoassy(Enzygnost^R anti-H. pylori lgG kit). To determine the sensitivity and specificity of the serologic test, CLO test, culture and histopathology were used as reference tests for the diagnosis of anti-H. pylori infection.

The anti-H. pylori lgG antibody was positive(cutoff value ; 10U/mL) in 91 among 151 patients(60.3%). The positive rate of anti-H. pylori lgG showed slightly increasing tendency by age until the 6th decade of age(0% in 2nd decade, 52.4% in 3rd, 59.5% in 4th, 62.1% 5th, 67.8% in 6th 60.9% in 7th and 66.7% in 8th decade). According to the endoscopic diagnosis the positive rate of anti-H. pylori lgG was 61.1% in active duodenal ulcer, 63.2% in gastric ulcer, 64.6% in gastritis and 61.5% in gastric cancer, but it was only 25% in ednoscopically normal patients, which was significantly lower than active duodenal ulcer(p<0.05), gastric ulcer(p<0.05) and gastritis(p<0.05) patients. The concordance rate between anti-H. pylori lgG and COO test was 59.6%. Using the cutoff value of anti-H. pylori lgG titer as 10U/mL, the sensitivity and specificity of serum anti-H. pylori lgG test were 61% and 30%, when 20U/mL, 35% and 60%, and when 50U/mL, 20% and 90% respectively.

The sensitivity and specificity of serum anti-H. pylori lgG test were low in this study. Even though it is an noninvasive test, we cannot rely on it without other invasive tests for the diagnosis of H. pylori infection.