Poster (15W161)

Accuracy of the CLO test versus histology in the diagnosis of Helicobacter pylori infection in patients undergoing gastroscopy at Tallaght Hospital

Author(s)

Denise Brennan, Turlough Heffernan, Joseph Omorogbe, Mary Hussey, Grainne Holleran, Vikrant Parihar, Yousif Hamid, Colm O’Morain, Sinead Smith*, Deirdre McNamara*

Department(s)/Institutions

Trinity Academic Gastroenterology Group (TAGG), Department of Clinical Medicine, Trinity College Dublin. *Joint senior authors

Introduction

The accurate detection of H. pylori infection is essential for managing infected patients with gastro-duodenal symptoms. The reduced prevalence of infection in the developed world and the widespread use of PPI’s can affect the accuracy of a given diagnostic test in terms of sensitivity and specificity. Commonly employed tests for H. pylori on gastric biopsies include the Campylobacter-like organism (CLO) test, histological examination and culture.

Aims/Background

To determine the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the CLO test versus histological testing for the detection of H. pylori infection.

Method

Adult patients were prospectively recruited to the study from our endoscopy department from April 2013 to July 2015. Following ethical approval and informed consent, gastric biopsy samples were obtained from patients undergoing endoscopy. For CLO testing, a biopsy was taken from the antrum (from April 2013 to October 2014, single antral biopsy used in CLO test; from October 2014 to July 2015, combined antral and corpus biopsies used in CLO test). CLO tests were stored at room temperature and examined and interpreted after 30 minutes in accordance with manufacturer‘s guidelines. An additional two biopsies each were taken from the antrum and corpus for histological examination for H. pylori by hematoxylin and eosin staining and immunohistochemistry. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the CLO test was compared to histology using Diagnostic Test Evaluation software (www.medcalc.org).

Results

In all, 473 patients mean age 52.7±16.8 years, 45% (n=213) male were included. A total of 98 (20.7%) patients were positive by histology while 99 (20.9%) patients were positive by CLO test. The average age of infected patients (by histology) was 49.4±15 years, 51% (n=50) male, while the average age of noninfected patients was 53.6±17.1 years, 43.5% (n=163) male. Patients infected with H. pylori were significantly younger than those who were not (49.4 vs 53.6 years; p= 0.03; 95% CI 0.5025 to 7.962). Using histological testing as gold standard, there were 21 false positive and 20 false negative CLO tests. The sensitivity, specificity, PPV and NPV of the CLO test compared to histology was 80%, 94%, 79% and 95% respectively.

Conclusions

The rate of patients infected with H. pylori attending Tallaght Hospital is low (20.9%, by histological testing). The low sensitivity and NPV of the CLO test (80% and 79% respectively) warrants continued histological testing for H. pylori in order to ensure minimal incidence of false negative diagnosis. It is necessary to continue use of the CLO test during endoscopy because it allows prompt diagnosis of infection, on the same day the procedure is carried out.