Regular arrangement of collecting venules and the Kimura‐Takemoto classification for the endoscopic diagnosis of Helicobacter pylori infection: Evaluation in a Western setting

The regular arrangement of collecting venules (RAC) and the Kimura‐Takemoto classification of atrophic change (KTC) are simple and easy‐to‐use criteria which have been shown to reliably predict or rule out a Helicobacter pylori infection of the stomach. Although these features have been investigated extensively in Asia, their significance in the West has not been evaluated.


INTRODUCTION
V ARIOUS ENDOSCOPIC CRITERIA have been described to predict or rule out a Helicobacter pylori infection of the stomach. An easily detectable feature of a healthy stomach without H. pylori infection is the regular arrangement of collecting venules (RAC). Multiple publications on RAC have shown a high sensitivity and specificity for the prediction of H. pylori uninfected stomachs. For example, Yagi et al. 1 demonstrated a sensitivity of 93.8% and specificity of 96.2% of RAC in the identification of the normal stomach without H. pylori. On the other hand, the irregular arrangement of collecting venules or its absence is significantly associated with H. pylori infection of the stomach. This has also been demonstrated in various publications with excellent sensitivity and specificity values of about 90%. 2,3 The collecting venules can be described as minute red spots on the mucosal surface. In the close-up view, they have a starfish like appearance. In the normal stomach without H. pylori infection, inspection of the body shows a regular arrangement of these collecting venules ( Fig. 1) while the H. pylori infected stomach is expected to have an irregular arrangement or absence of these venules (Fig. 2). A further criterion closely associated to H. pylori infection is the degree or severity of atrophy of the gastric mucosa. 4 The endoscopic evaluation of atrophic change, initially described by Kimura and Takemoto,5 can be simplified to include two grades: closed type atrophy, where atrophic change is limited to the lesser curvature, as well as open type atrophy, where atrophic change includes both the lesser and the greater curvature of the stomach body. In the Kyoto classification of gastritis, various endoscopic features have been evaluated to be associated with H. pylori infection. [6][7][8] These features include atrophy, intestinal metaplasia, enlarged folds, nodularity of the mucosa and diffuse redness with or without the presence of RAC. Basically, a Kyoto classification score of ≥2 indicates H. pylori infection while a score of 0 indicates no H. pylori infection. 7,8 All the studies mentioned above were done predominantly in Asia. The question we sought to answer in this study, was the significance of RAC and Kimura-Takemoto classification of atrophic change (KTC) as well as the endoscopic features described in the Kyoto classification in the endoscopic prediction of H. pylori infection in a Western population. This report is the first to evaluate RAC, KTC and other endoscopic features of the Kyoto classification of gastritis for the diagnosis of H. pylori infection in Europe.

I N 200 CONSECUTIVE gastroscopic examinations per-
formed by an experienced endoscopist in a German tertiary care center, the results of RAC and KTC were noted. All patients gave written informed consent prior to the intervention. The study was conducted in accordance with the ethical principles of the Declaration of Helsinki and in compliance with good clinical practice and local regulations and was approved by the Institutional Review Board. Prior to data collection, the endoscopist was trained in the diagnostic skill of recognition and description of RAC and KTC by experienced Japanese endoscopists. All examinations were done in the endoscopy unit of the University Hospital Augsburg. Patients included in the study underwent gastroscopy for a variety of reasons. The indication for gastroscopy did not influence inclusion or exclusion from the study. However, patients with a prior history of H. pylori infection or of eradication therapy were excluded from the study. Patients with hypertensive gastropathy as well as patients with a contraindication for biopsy of the stomach were also excluded. All patients were above 18 years of age. The presence or absence of RAC at the gastric angle was noted prospectively. Additionally, a simplified version of the Kimura-Takemoto classification (KTC) was recorded. According to Kimura and Takemoto, the closed type is further subdivided into C-1, C-2 and C-3 while the open type is further subdivided into O-I, O-II and O-III. However, for the purpose of this study, two groups for the KTC were formed: non-atrophy/ C1 (Fig. 3) and atrophy ( Fig. 4) including C-2/C-3 and O-1/O-2/O-3. All examinations were done with an Olympus GIF-180 or GIF-190 gastroscope (Olympus Medical Systems, Tokyo, Japan). For each patient, biopsies to determine the H. pylori infection status using histology or the urease test were taken. For histology, H&E as well as Giemsa staining was performed. Two biopsies (lesser and greater curvature) were taken from the antrum and from the body, respectively, while the urease test was done using one biopsy from the antrum and one further biopsy from the body of the stomach. Patients with a positive histology or a positive urease test or a positive histology and a positive urease test were considered H. pylori positive while those with a negative histology and urease test were considered as H. pylori negative. The urease test was left to develop a color change for a maximum time of 24 h. Finally, a multivariate analysis to determine the most important endoscopic features of the Kyoto classification criteria 9 which were associated with endoscopic diagnosis of H. pylori infection was performed.

Data analysis
For the statistical analysis, a simple two-by-two table was used to calculate the sensitivity, specificity, positive predictive value (PPV) and negative predictive values (NPV) for RAC and KTC as predictors of H. pylori infection. Also, a pooled analysis of RAC and KTC was done, combining both  parameters for the prediction of H. pylori infection. Additionally, a subgroup analysis of patients who were not on proton-pump-inhibitors (PPI; n = 95) was performed, also using a two-by-two table as described above. Furthermore, an assumption of H. pylori prevalence rate in an adult German population of about 40% was used. 10,11 Additionally, sensitivity and specificity values of 90% for the gold standard (histology/urease test) were assumed because of literature reports which have shown these values to be in a range between 80% and 98%. 11 As such, calculations using an assumption of a conditional independence and known sensitivities and specificities of the reference standard using a frequentist maximum likelihood method were performed. 12 For multivariate analysis, a stepwise logistic regression model was implemented.  (Table 3). When the reference standard is considered "imperfect" and an assumption of a conditional independence is utilized the sensitivity and specificity for RAC was 88% and

DISCUSSION
I N GENERAL, THESE results show excellent sensitivity as well as negative predictive values for RAC, KTC and RAC/KTC in a randomly selected patient population as well as in the subgroup analysis of patients without PPI medication. This means that RAC, KTC and RAC/ KTC predicted H. pylori negativity in uninfected patients correctly in a high proportion of cases. Furthermore, multivariate analysis of the endoscopic criteria described by the Kyoto classification of gastritis showed that both atrophy as well as diffuse redness without RAC were the most important factors associated with the presence of H. pylori infection. Although the specificity and positive predictive values seen in this study are not quite as high as in the Asian study reports mentioned above, 1-3 these results should still be considered as satisfactory for a single examiner study in a Western setting. Furthermore, when an assumption of a conditional independence and known sensitivities and specificities of the reference standard using a frequentist maximum likelihood are utilized, then sensitivity and specificity values improved considerably. Endoscopists should be aware of macroscopic features and mucosal changes which could be     13,14 In such cases, it has been recommended to stop PPI at least 2 weeks before performing H. pylori testing. The use of endoscopic criteria such as RAC or KTC to predict H. pylori infection is not affected by on-going PPI treatment. As such, these criteria can be considered when patients with PPI undergo negative H. pylori testing, especially when there is suspicion of false-negative testing. For RAC assessment, endoscopists should be aware that RAC may be observed in the upper part of the stomach if the atrophy of the gastric mucosa has not progressed proximally, even if the patient is infected with H. pylori. This may have reduced the accuracy of RAC assessment in this study. The study limitations in our study include the single examiner/single center modus of data collection as well as the small sample size which may have limited the statistical power especially in the subgroup analysis of patients who were not on PPI medication. It would have been preferable to evaluate these criteria on a larger scale in multiple centers and by multiple examiners with different levels of endoscopy experience. Also, the determination of H. pylori infection using biopsies of the antrum and body may have been improved if an additional biopsy point at the incisura angularis was included and as recommended by the updated Sydney classification. In conclusion, we have been able to show that RAC and KTC are macroscopic parameters which should be given attention during routine endoscopy. These features are especially good in the prediction of H. pylori uninfected stomachs. Further data analysis needs to be done on a larger study population and in a multicenter approach.

O PEN ACCESS FUNDING enabled and organized by
Projekt DEAL.

CONFLICT OF INTEREST
A UTHORS DECLARE NO conflicts of interest for this article.

FUNDING INFORMATION
N O FUNDING WAS received for this study.