Comparison of different cytological tools with conventional diagnostic methods in diagnosis of Helicobacter pylori infection

Background: Helicobacter Pylori (H pylori) infection causes severe gastrointestinal morbidity and mortality worldwide. Objective: To evaluate the usefulness of gastric crush cytology and imprint cytology with conventional histopathology and rapid urease tests. Materials and Methods: Antral biopsies were collected from 130 patients and evaluated for H Pylori infection by imprint cytology, crush cytology and histopathological examination by different stains and rapid urease test. Results: 118 patients showed H. pylori infection by two or more methods. Giemsa histology, showed highest sensitivity, specificity, Positive predictive value (PPV), negative predictive value (NPV) and Youden’s index (YI). Among cytology methods, crush cytology was found more effective in detecting H pylori infection. Conclusion: H. pylori infection is associated with gastric mucosa changes like chronic active gastritis, atrophy, intestinal metaplasia, ulceration and carcinoma. Imprint cytology has high sensitivity and comparable predictive values to conventional diagnostic tools-histopathological examination and rapid urease test in detection of H. pylori infection.


Introduction
H pylori infection is recognised one of the most important causative factor of gastroduodenal diseases. The prevalence of H Pylori infection shows marked geographical variation with maximum prevalence in developing countries [1]. The annual incidence of H Pylori infection is 0.3 to 0.7% in developed countries and 6-14% in developing countries [1].Various invasive and non invasive tests are employed for detection of H Pylori infection. Non invasive tests include urea breath tests, serological test-IgG, IgM detection, salivary and urinary antibodies test and stool antigen test [3]. The invasive tests are endoscopy based tests, which include histipathological examination, cytological examination-Crush and imprint cytology, rapid urease test (RUT) and polymerase chain reaction. Cytological examination, such as imprint and crush smears have been used in detection of malignancy with sensitivity up to 95.2% [4]. These techniques are routinely not used in detection of H pylori infection. So we evaluated the usefulness of imprint and crush smears with conventional histopathological examination and RUT.

Material and Methods
The patients were selected on the basis of chief complaints of dyspepsia and the age of patients ranged from 14 to 86 years. Certain exclusion criteria were applied such as patients on proton pump inhibitor (PPI) therapy or any antibiotic therapy within last one month. Endoscopy was carried out using "Pentax'' forward viewing oesophago gastro duodenoscope. The patients were taken for upper G.I. Endoscopy after making them fast overnight. The endoscopy was considered normal on visualizing mucosa which is pink in colour, smooth and lustrous 130 patients undergoing upper gastrointestinal endoscopy in the hospital-Sree Narayana Institute of Medical Sciences, Ernakulam, Kerala, India were enrolled in this prospective type of study. Three different diagnostic methods were usedhistology, cytology (Imprint and crush) and RUT. Three antral biopsy fragments were obtained from each patient and two samples sent for pathological examination in unfixed state and one sample being sent for RUT. Imprint smears were prepared from one fragment by keeping one fragment on a glass slide and gently touching it without pressing. Imprint slides were On another biopsy fragment, RUT was performed by following method -Urea (2 g) was dissolved in 20 ml double distilled water. 20 drops of phenol red was added to the solution and pH was adjusted between 6.8 and 6.9 by adding a drop of N/10 HCl, if pH was greater or N/10 Na NaOH, if pH was less. Solution was having faint yellow tint at this stage.
This was transferred to sterile vial each containing 2 ml in each vial. Biopsy material was added and the temperature was kept constant at 35-37°C. Test was considered positive, if colour changed within 30 minutes and weekly positive, if the change occurred after 2 hours.
Histopathological changes of gastric mucosa were also assessed. Lymphoplasmacytic infiltrates without neutrophilic infiltration was regarded as chronic gastritis and with neutrophilic infiltration as chronic active gastritis. Atrophy of glands was regarded as atrophic gastritis and goblet cell metaplasia of glandular lining was regarded as intestinal metaplasia. Density of H. pylori was assessed according to visual analogue scale of updated Sydney grading system [5]. To increase the accuracy and prevent bias, positivity for two or more methods (by any of the stains, RUT) was considered as true positive. Sensitivity, specificity, PPV and NPV of different methods were computed and compared. Youden's index = Sensitivity + Specificity − 100. Informed consent was taken from each patient and the study was approved by scientific research committee of the institution.  patients, chronic gastritis in 20 patients, chronic active gastritis with intestinal metaplasia in 12 patients, chronic follicular gastritis in 10 patients and ulcerative changes in 6 patients. Dysplastic changes were not seen in any patient. Normal mucosal study was seen in 6 patients.

Discussion
H. pylori infection is associated with varying degree of inflammation and architectural distortion in different individuals. This variability is not only accounted by the variation in bacterial load/density, but also relies on immunogenicity of host/patient. In 2% of cases, H. pylori infection leads only to mild chronic gastritis or almost unremarkable mucosal change [5,6] [8] reported equal sensitivity and specificity of imprint cytology as that of biopsy examination. When evaluated in terms of YI, highest YI was found for Giemsa histology. YI validates a technique by taking both sensitivity and specificity into account. Low NPV noted in this study for different methods can be attributed to false negative cases reported. Low bacterial load and multifocality of the bacteria can lead to false negative cases in cytological smears, as sparse H. pylori are difficult to interpret amidst the dirty background of smears.While imprint cytology represents the superficial part of the biopsy, crush cytology represents entire biopsy specimen and has comparable sensitivity and specificity to histopathology. Even in histopathology examination, specimen processing can lead to false negative result due to partial loss of area in or beneath the surface mucosal layer, especially in set up of low bacterial density [8,9]. This is in concordance with the present study findings, as all false negative cases seen in different methods, had low H. pylori density.

Conclusion
Cytological tools-Imprint cytology and crush cytology are rapid inexpensive methods of diagnosing H. pylori infection. It has comparable predictive values to histopathological examination and RUT. Cytological smear examination and biopsy should be used in conjunction, as rapid diagnosis and architectural assessment of gastric mucosa is essential for effective management of the patient.
Funding: Nil, Conflict of interest: None initiated, Permission from IRB: Yes