This prospective, multi-center clinical trial was performed between July 2014 and May 2016 in 14 tertiary hospitals distributed throughout Korea.13 All patients underwent screening gastroscopy for the identification of organic disease and completed a questionnaire prior to treatment commencement. Inclusion criteria were age ≥18 years, a diagnosis of FD in accordance with the Rome III criteria, and H. pylori-positivity as determined one of the following three methods: 1) the rapid urease test (CLOtest®; Delta West, Bentley, Australia); 2) the ¹³C-urea breath test (¹³C-UBT, UBiTkit; Otsuka Pharmaceutical Co., Ltd., Tokyo, Japan); or 3) histologic confirmation of H. pylori by modified Giemsa staining. The exclusion criteria applied were: 1) an age of <18 years; 2) endoscopically confirmed structural disease (e.g., erosive esophagitis, peptic ulcer, mucosa-associated lymphoid tissue lymphoma, or dysplasia) but no gastritis or intestinal metaplasia; 3) history of gastric surgery; 4) gastric cancer or another malignancy; 5) previous H. pylori eradication therapy; 6) abnormal liver or renal function; 7) liver cirrhosis or chronic kidney disease or another uncontrolled concurrent disease; 8) pregnancy, lactation, or refusal to use contraception during the study period; 9) a drug history that might have affected eradication results, such as proton pump inhibitor (PPI), H2 receptor antagonist, mucosal protective agent, or antibiotics during the prior four weeks prior to study commencement; 10) a genetic or mental disorder or alcohol or drug addiction; 11) history of drug allergy or any specific contraindication for study drugs; or 12) any condition that might influence clinical results (as determined by the principal investigator), such as a well-controlled underlying cardiological, respiratory, or gynecological disease.

This study protocol was approved beforehand by the Korean Food and Drug Administration (KFDA No. 30157) and by the Institutional Review Boards and Ethics Committees of all hospitals involved, which included Seoul National University Bundang Hospital (IRB number: B-1403/234-003). Written informed consent was obtained from all patients prior to enrollment, and the study was conducted according to Good Clinical Practices and the Declaration of Helsinki. The study protocol was registered at ClinicalTrials.gov and the Clinical Research Information Service as a secondary outcome measure of NCT02159976 and KCT0001176.

The questionnaire requested demographic data, BMI, smoking (never smoker/ex-smoker/current smoker) and alcohol (never drinker/ex-drinker/current drinker) habits, and details of comorbidities and of the Rome III criteria of FD.1 The Korean version of the questionnaire used was derived by translation from the original Rome III FD module and has been validated.14 Briefly, the questionnaire consisted of 11 questions, which addressed the presence of FD and the severities of symptoms using symptom frequencies. FD was defined as the existence of one or more of the following symptoms: 1) bothersome postprandial fullness; 2) early satiation; 3) epigastric pain; or 4) epigastric burning for at least the previous three months with a symptom onset at least six months prior to diagnosis based on Rome III criteria. In the questionnaire, FD was classified as postprandial distress syndrome (PDS) or epigastric pain syndrome (EPS). PDS was defined as the existence of one or both of the following symptoms: 1) bothersome postprandial fullness occurring after ordinary sized meals at least several times per week or 2) early satiation preventing complete consumption of a regular meal at least several times per week. EPS was defined as the existence of all of the following symptoms: 1) pain or burning of at least moderate severity localized to epigastrium at least once per week; 2) pain not relieved during the same day; and 3) pain not relieved by defecation or flatus. In addition, patients that met the criteria for PDS and EPS were assigned to a PDS/EPS group. Patients were also required to rate baseline symptom severity using a 5-point Likert scale: 1. minimal discomfort, 2. mild discomfort, 3. moderate discomfort, 4. severe discomfort, 5. very severe discomfort.

Patients were requested to revisit one year after H. pylori eradication commencement when patients completed the same questionnaire and were evaluated to assess symptom improvements. When a patient was unable to visit hospital, the questionnaire was completed by phone. Dyspeptic symptom responses were classified as; complete response (>75% symptom resolution), satisfactory response (≥50% but <75%), partial response (≥25% but <50%), and refractory response (<25% symptom resolution). Patients with ‘complete’ or ‘satisfactory’ response were defined as responders, and those with ‘partial’ or ‘refractory’ response were defined as poor responders.11 During the follow-up period, the patients were allowed to take prescribed drugs for symptom control after completing H. pylori eradication therapy, but these medication histories were recorded.

H. pylori infection statuses were determined by Giemsa staining or by using the rapid urease test (CLOtest®) or the ¹³C-urea breath test (¹³C-UBT, UBiTkit). Four gastric mucosal tissues (from the greater and lesser curvatures of antrum and corpus) were acquired from each patient by forceps biopsy during endoscopy and fixed in formalin for Giemsa staining. Two additional gastric mucosal tissues from the lesser curvature of antrum and corpus were used for rapid urease testing (CLOtest®).

Patients fasted for at least four hours prior to the ¹³C-urea breath test (¹³C-UBT, UBiTkit). Briefly, after obtaining an initial breath sample, patients drank 100 mL water containing 100 mg of ¹³C-urea powder (UBiTkit™; Otsuka Pharmaceutical Co., Ltd.), and 20 minutes later a second breath was obtained. H. pylori infection status was determined using an isotope ratio mass spectrometer (UBiT-IR300; Otsuka Electronics, Osaka, Japan) using the obtained breath samples. The cut-off value of the procedure was 2.5%.

Initially, patients were randomized to receive sequential therapy for 10 days or modified bismuth quadruple therapy for 14 days.13 If a patient failed to achieve eradication after 10 days on sequential therapy or 14 days on modified bismuth quadruple therapy and requested a second-line eradication therapy, quinolone-based triple therapy or traditional bismuth quadruple therapy was recommended. ¹³C-urea breath testing (¹³C-UBT, UBiTkit) was conducted to determine H. pylori eradication status four weeks after treatment completion.

The statistical analysis was performed using the SPSS version 20.0 (SPSS Inc., Chicago, IL, USA). Categorical variables were analyzed using Pearson's chi-square (χ²) test or Fisher's exact test and results are presented as numbers (percentages). Continuous variables were analyzed using the Student's t-test and results are presented as means±standard deviations. Univariate and multivariate logistic regression analyses were used to identify risk factors; results are expressed as ORs and 95% CIs. Statistical significance was accepted for p-values <0.05.

Sixty-five H. pylori-infected treatment-naïve patients with FD were enrolled in the present study (Fig. 1). Mean age of the 65 patients was 51.9 years (range, 23-76 years), and 33 (50.8%) were women. Numbers of patients with PDS, EPS, or overlapping PDS/EPS were 53 (81.5%), 43 (66.2%), and 31 (47.7%), respectively. Other clinical data and personal health habits are detailed in Table 1.

One patient of the 65 patients was lost to follow-up. Of the remaining 64 patients, 56 (87.5%) achieved eradication success, and of the eight patients in whom eradication therapy failed, six received second-line eradication therapy and two refused further treatment. Of these six patients, five (83.3%) achieved eradicated success after second-line eradication therapy. Therefore, 61 patients (95.3%) were allocated to the H. pylori-eradicated group and three (4.3%) to the H. pylori-persistent group. However, one patient in the H. pylori-eradicated group could not be contacted for the one-year symptom assessment (Fig. 1).

FD response rates at one year in the H. pylori-eradicated (n=60) group were 75% for responders (complete or satisfactory FD response) and 25% for poor responders (partial and refractory FD response) and in the H. pylori-persistent (n=3) group were 0.0% and 100.0%, respectively (p=0.021) (Table 2).

Of the 64 patients, 10 (15.6%) received medication during follow-up. Mean prescription period was 2.3 months (range, one to 9.5 months). More specifically, four patients (6.3%) received a prescription for one month, five (7.8%) for two months, and one (1.6%) received a prescription for 9.5 months. None of these patients had taken a prescribed drug during the two weeks before one-year assessments. Regarding types of drugs taken, two patients took PPIs, two PPIs and antacids, two PPIs, antacids, and prokinetic agents, one took a prokinetic agent, and other three took antacids and prokinetic agents.

The predictive factors for poor FD response at one year are presented in Table 3. Univariate analysis showed H. pylori persistence (p=0.021), a female gender (p=0.025), and receipt of medication (p=0.013) were significantly associated with poor response, and that age, smoking, alcohol consumption, the presence of an underlying disease (e.g., diabetes mellitus and hypertension), type of eradication therapy, FD subtype, and baseline symptom severity were not associated with poor FD response. Multivariate analysis with respect to age, gender, BMI, diabetes mellitus, hypertension, and overlapping PDS/EPS showed only a female gender (OR, 4.70; 95% CI, 1.17-18.88) was independently related with poor FD response at one year. Unfortunately, multivariate analysis computation of the OR for H. pylori eradication was not possible because there was no H. pylori-persistent patient in the responder group.