Correlation of H. pylori Antigen Titer with Digital Polymerase Chain Reaction Quantification: Analytical Evaluation...

The standardization of Helicobacter pylori (H. pylori) diagnosis remains challenging across heterogeneous detection assays. Immunochromatography detects H. pylori-specific antigens but delivers only qualitative results, susceptible to interference from non-target soluble bacterial proteins via non-specific binding or competitive inhibition. By contrast, digital PCR (dPCR) enables precise quantification of genomic DNA copies, identifying both viable and non-viable bacteria. This study compared immunochromatography-derived endpoint titers (semi-quantitative values calculated as the reciprocal of the highest detectable two-fold serial dilution) with dPCR-quantified nucleic acid copy numbers. Twenty-four H. pylori bacterial suspensions, cultured for 72 h at 37 °C on Brucella agar supplemented with 5% defibrinated sheep blood under microaerophilic conditions (85% N2, 10% CO2, 5% O2), were subjected to parallel antigen testing and dPCR measurement. Pearson correlation and linear regression were applied for statistical evaluation. We observed a significant positive correlation between antigen titer and genomic copy number (r = 0.536, n = 24, P = 0.007). However, the low coefficient of determination (R² = 0.287) demonstrated limited predictive power, as antigen titer accounted for merely 29% of dPCR-measured variance and cannot support robust single-sample prediction. Discordant high-dPCR/low-titer profiles may originate from non-viable bacterial debris or free genomic DNA. Antigen-based and nucleic-acid-based assays quantify biologically related yet non-interchangeable analytes. Multi-parameter characterization combining colony-forming units, antigen titers and genome copy numbers is suggested for reference material development and diagnostic-assay validation. This work highlights the requirement for H. pylori-specific consensus guidelines to resolve diagnostic discrepancies.