Design and population
This cross-sectional study was approved by the Ethics Committee of the Ardabil University of Medical Sciences. Patients presenting with functional dyspepsia to the referral gastroenterology outpatient clinic of Imam Khomeini Hospital in Ardabil, Iran between Jun 2015 and March 2016 were recruited for the study subjects. Written informed consent was obtained from all participants.
Functional dyspepsia was diagnosed if a patient met all of the following criteria: persistent or recurring dyspepsia for more than 3 months within the past 6 months; the absence of a possible organic cause of the symptoms on endoscopy; and without any sign that the dyspepsia is diminished only by defecation or of a correlation with fecal irregularities.
A total of 200 participants with functional dyspepsia who had a negative stool exam for Helicobacter pylori antigen were included in this study. All patients were assessed by a thorough history, physical examination, and routine laboratory investigations. In order to evaluate the cause, the patients were a candidate for endoscopy based on the opinion of the gastroenterologist. The criteria for entering the study were only those who complained of functional dyspepsia with negative stool antigen test, negative rapid urease test, and normal upper gastrointestinal endoscopy.
Patients who met the following criteria were excluded from the study: (1) a positive H. pylori infection using a positive stool antigen test; (2) a positive H. pylori infection using a rapid urease test and histology; (3) a history of hospitalization for ≤1 month before the study; (4) evidence of biliary disease at ultrasonography; (5) receiving antacids, non-steroidal anti-inflammatory drugs, antibiotics, bismuth, or proton-pump inhibitors within the prior 4 weeks; (6) past medical history of H. pylori-eradication therapy; and (7) Unwillingness to participate in the study.
H. pylori stool antigen test
The H. pylori stool antigen test, using a monoclonal antibody-based sandwich enzyme-linked immunosorbent assay, was used to analyze the stool samples.
Upper gastrointestinal endoscopy
The standard upper gastrointestinal endoscopy was performed with a Pentax EG-2990K Video Gastroscope (Pentax Medical Company, Tokyo, Japan) after overnight fasting by two experienced gastroenterologists. Multiple biopsy specimens were obtained from the antrum of the stomach for rapid urease test (Kimberly-Clark, CLO test, Rapid Urease Test Gel, GA 30076-2199 USA) and histology.
H. pylori serological assessment
Patients who were negative in terms of stool antigen test and rapid urease test, and had no obvious gross pathologic sign in gastroduodenoscopy were considered suitable candidates for serological study. The method used for serum analysis of the samples was based on Enzyme-Linked Immunosorbent Assay techniques (ELISA) and the use of the commercial kits for IgG assay (ElAgen, Clone system S.P.A., Casalecchio Di Reno, Italy). This assay system was based on the qualitative detection of lgG specific antibodies to H. pylori. The cut-off values of more than 15 arbitrary units (AU) per milliliter (ml) were considered as a positive test. The advantage of serological tests is based on the findings of anti-H. pylori antibodies is that are less likely to be confounded by suppression of H. pylori infection by medications.10
The results were expressed as means ± standard deviations (SD). The statistical analysis of the data was done using SPSS software (version 21, SPSS Inc., Chicago, IL, USA). A value of P < 0.05 was considered significant.