Saliva or serum, which is better for the diagnosis of gastric Helicobacter pylori infection?

Helicobacter pylori is known as an agent which may involve in the occurrence of peptic ulcer, gastric cancer and also other known and unknown diseases. Treatment of the infection with antibiotics eradicates the disease and prevents its pathologic effects. A noninvasive and inexpensive method for detection of the infection is needed. In this study the diagnostic values of serum and saliva anti H. pylori IgG was evaluated.Patients and The saliva and blood samples were collected from 114 patients who underwent upper GI endoscopy and gastric biopsy. Tissue samples were examined by rapid urease test and microscopic study. Saliva and serum samples were tested by ELISA-based test for anti H. pylori IgG, using a commercial kit. From 114 cases, 61(53.5%) patients were positive for H. pylori in rapid urease test and microscopic study and 53(46.5%) were negative in both tests. Rates of positive result for H. pylori in patients with and without peptic ulcer were almost similar. Mean values of anti H. pylori IgG in saliva and serum of H. pylori positive patients were higher than H. pylori negative patients. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy of tests in saliva were 83.6%, 71.7%, 77.3%, 79.1%, 78.1% and in serum were 90.2%, 86.8%, 88.7%, 88.4% and 88.6% respectively. It was concluded that ELISA-based anti H. pylori IgG test in saliva could be used as an alternative diagnostic test in the absence of other invasive procedures.