Diagnostic Accuracy of Various Genetic Markers (tpi, gdh, and bg) for Prevalence and Genotyping of Giardia duodenalis in Human Samples: A Comparative Global Systematic Review and Meta-Analysis.

Background: Giardia duodenalis is a widespread intestinal protozoan causing giardiasis in humans and animals. Precise detection and genotyping of this parasite are vital for understanding its epidemiology, implementing appropriate treatments, and mitigating transmission. Molecular techniques, particularly multilocus genotyping (MLG) targeting the beta-giardin (bg), triose phosphate isomerase (tpi), and glutamate dehydrogenase (gdh) genes, have improved diagnostic precision. However, variations in sensitivity and diagnostic performance among these genes can influence prevalence rates and genotyping results, particularly for assemblages A and B, the most common in humans.

Methods: This study evaluated the pooled prevalence of G. duodenalis in human samples confirmed positive by microscopy and/or small subunit ribosomal RNA (SSU rRNA), using bg, tpi, and gdh genes. A comprehensive literature search identified 32 studies with MLG design published up to January 13, 2025, encompassing 96 datasets from 21 countries on four continents. Data extraction and quality assessments were conducted independently by two reviewers. Meta-analyses employed a random-effects model using CMA software, with heterogeneity assessed via the I² statistic.

Results: Pooled prevalence and diagnostic accuracy were highest using the tpi gene (64.3%; 95% CI: 56.1-71.8%), followed by gdh (59.7%; 95% CI: 51.8-67.1%) and bg (58.3%; 95% CI: 49.8-66.3%). Nonetheless, a notable fraction of microscopy- and/or SSU rRNA-confirmed samples were undetected by these loci. Assemblage B was more prevalent than A across all genetic markers. The gdh gene showed superior sensitivity for assemblage B (59.5%), whereas bg had a slightly higher detection rate for assemblage A (41.6%). These findings underscore the importance of using multiple genetic markers for precise detection and genotyping. The tpi gene offers the highest sensitivity for overall prevalence among Giardia-positive samples, while gdh and bg contribute critical assemblage-specific insights.

Conclusion: The higher prevalence of assemblage B underlines the need for targeted public health strategies, especially given its association with more severe or recurrent infections. Overall, integrating MLG with SSU rRNA analysis is essential for improving diagnostics, surveillance, and control strategies for giardiasis globally.