Real-Time PCR for Diagnosing Helicobacter pylori Infection in Patients with Upper Gastrointestinal Bleeding: Comparison with Other Classical Diagnostic Methods

Abstract

The aim of this study was to determine the diagnostic usefulness of quantification of the H. pylori genome in detection of infection in patients with upper gastrointestinal bleeding (UGB). A total of 158 consecutive patients with digestive disorders, 80 of whom had clinical presentation of UGB, were studied. The number of microorganisms was quantified using a real-time PCR system which amplifies the urease gene with an internal control for eliminating the false negatives. A biopsy sample from the antrum and corpus of each patient was processed. The rapid urease test, culture, histological study, stool antigen test, and breath test were done. The gold standard was a positive culture or positive results in at least two of the other techniques. When a positive result was defined as any number of microorganisms/human cell, the sensitivity of real-time PCR was greater in bleeding patients, especially in the gastric corpus: 68.4% (95% confidence interval [CI], 52.3 to 84.5%) in non-UGB patients versus 91.5% (95% CI, 79.6 to 97.6%) in UGB patients. When a positive result was defined as a number of microorganisms/human cell above the optimal value that maximizes the Youden index (>3.56 microorganisms/human cell in the antrum and >2.69 in the corpus), the sensitivity and specificity in UGB patients were over 80% in both antrum and corpus. Our findings suggest that some bleeding patients with infection caused by H. pylori may not be correctly diagnosed by classical methods, and such patients could benefit from the improved diagnosis provided by real-time PCR. However, the clinical significance of a small number of microorganisms in patients with negative results in classical tests should be evaluated.

Role of Helicobacter Pylori stool antigen test in the diagnosis of Helicobacter Pylori infection

“…Lower sensitivity for HpSA is also shown in patients with upper GI bleeding. 24 In order to limit these possibilities, we excluded GI bleeding patients as well as patients with diarrhea which makes our results more accurate. However, the limitation of the study was the small number of cases.…”

Specific Conditions: Diagnosis of H. pylori Infection in Case of Upper Gastrointestinal Bleeding

“…It has been also reported that Real-time PCR can improve H. pylori detection rate in a histology-negative, formalin-fi xed, and paraffi nembedded tissue [ 33 ]. Since the newly developed quantitative real-time PCR is around ten times more sensitive than the conventional PCR method [ 34 ], real-time PCR in diagnosis of H. pylori infection in patients with UGI bleeding could be useful diagnostic methods with increase in sensitivity and additional gain of bacterial load [ 35 ]. However, further study about the cut-off value which can distinguish the real infection from asymptomatic colonization is warranted.…”

Diagnóstico rápido de las infecciones del tracto gastrointestinal por parásitos, virus y bacterias

“…Desde hace muchos años se han utilizado métodos moleculares caseros para el diagnóstico de la infección por H. pylori a partir de diferentes muestras como biopsia gástrica, heces, saliva, jugo gástrico, etc. Además, permiten el estudio de mutaciones de resistencia a macrólidos como claritromicina (gen 23S ARNr), fluoroquinolonas (gen gyrA), tetraciclinas (gen 16S ARNr), rifabutina (gen rpoB) y amoxicilina (gen pbp-1a) 41,42 , y tienen las ventajas de la rapidez, de la mayor sensibilidad que el cultivo con métodos fenotípicos de sensibilidad a antibióticos, y detectan resistencia heterogénea, que puede ser difícil de obtener por cultivo 39,43 .…”