Giardiasis is an intestinal infection caused by a microscopic parasite called Giardia lamblia that affects millions of people worldwide. This infection causes diarrhea, abdominal pain, nausea, and fatigue. In children, untreated giardiasis can lead to malnutrition, growth delays, and developmental problems, making accurate diagnosis essential for proper treatment. Detecting giardiasis presents significant challenges for healthcare providers. The parasites are extremely small and can exist as either active forms in the intestines or dormant cysts shed in stool. When infections go undiagnosed, patients continue suffering while potentially spreading the infection to others. Three main diagnostic approaches are currently used. Traditional microscopic examination involves visually identifying parasites in stool samples under a microscope. This method is cost-effective but requires skilled technicians and often misses infections when parasite numbers are low. Rapid antigen tests detect specific proteins produced by the parasite, providing results within minutes but with variable reliability. Advanced molecular tests like PCR identify the parasite's genetic material with high accuracy but require specialized equipment and trained personnel. This research systematically analyzed 29 studies from Western Europe (2010-2023) to determine which diagnostic method performs best in European healthcare settings. The study compared how accurately different methods identified infections (sensitivity) and ruled out infections (specificity). The findings demonstrate that molecular PCR-based tests, particularly multiplex panels detecting multiple pathogens simultaneously, show superior accuracy, correctly identifying over 90% of infections. High-quality rapid antigen tests performed well, identifying 80-100% of infections, while traditional microscopic methods showed variable results depending on technique and operator expertise. The research concludes that molecular PCR-based methods should be the primary diagnostic approach in Western European clinical settings due to superior accuracy and rapid results. For epidemiological studies or resource-limited settings, quality rapid antigen tests offer practical alternatives. These findings support improved patient care through faster, more reliable diagnosis, reduced transmission, and better health outcomes. The research provides evidence-based guidance for healthcare providers choosing diagnostic methods, ultimately supporting better management of this common but often underdiagnosed infection.