Real-Time Polymerase Chain Reaction: Feed Two Birds with One Seed?

After Barry Marshall proved Helicobacter pylori as a pathogen of gastritis and peptic ulcers, antibiotic therapy is the most effective treatment for H. pylori infection. However, due to the increase in the antibiotic resistant H. pylori strains, eradicating H. pylori has been more challenging. The accurate diagnosis of H. pylori infection and detection of resistant strains is essential for improving the rate of H. pylori eradication. Although culture and antibiotic susceptibility tests based on culture are considered as reference methods for diagnosing infection and evaluating drug resistance, respectively, culturing H. pylori is technically demanding; it requires microaerophilic atmosphere and prolonged incubation time. Culture-based method takes approximately 2 weeks to decide H. pylori-negative. There are different success rates for culture depending on the laboratories. On the contrary, molecular techniques which mostly use polymerase chain reaction (PCR) have advantages over the conventional culture; the increase of sensitivity in detection (over 95%) and simultaneous detection of H. pylori and its resistances to clarithromycin and levofloxacin in a short time (<4 hours). In a recently published Korean study using dual priming oligonucleotide-based multiplex PCR, per protocol eradication rate for 7 days of tailored treatment with either bismuth quadruple therapy or standard triple therapy was 92.7% compared to 76.5% of the 7-day empirical standard triple therapy group. In terms of medical cost within Korea, the cost of tailored treatment was almost same as that of 14-day empirical standard triple therapy, and was not inferior in cost-effectiveness. However, while tailored treatment as a first-line based on clarithromycin resistance reported consistently a higher eradication rate than empirical triple therapy, it did not show superiority in treatment success in a rescue setting or compared to the bismuth quadruple therapy. In this context, the Korean College of Helicobacter and Upper Gastrointestinal Research recommends performing clarithromycin resistance test through PCR methods when selecting standard 7-day triple therapy as first-line treatment. Noh et al. showed real-time (RT)-PCR method (SeaSun Biomaterials) detection of H. pylori infection more efficiently 97.1% (68/70) compared to rapid urease test (82.9%, 58/70) using leftover specimens. RT-PCR also detected that 84.6% (11/13) of point mutations in 23S rRNA. The authors said RT-PCR-based assay is a simple and accurate method for detecting H. pylori and clarithromycin resistance using a small formalin-fixed or paraffin-embedded specimen. However, the failure to find point mutations in the two culture-proven resistant strains implies the RTPCR method has limitations in detecting only specific mutations like dual priming oligonucleotide PCR. In real practice, resistance or susceptibility tests are often required for patients who have failed the preceding eradication therapy, aside from the issue of the effectiveness of tailored therapy as a secondary treatment. The necessity of re-acquisition of gastric mucosa under endoscopy is the biggest hurdle to use resistant tests. Sensitive molecular methods using non-invasive specimens such as saliva can be a good alternative modality in the current circumstance where insurance coverage is the same as the indication for eradication. For now, PCR cannot completely replace the rapid ure-