This case study presents the application of the Karius Spectrum test in diagnosing pneumonia, particularly in immunocompromised patients. The study site was OSF Saint Francis Medical Center, where a 39-year-old patient with untreated HIV infection and respiratory failure underwent various tests, including the Karius Spectrum test, which identified Toxoplasma gondii as the causative agent. The patient was treated with pyrimethamine/sulfadiazine, resulting in significant clinical improvement. Additional clinical evidence from a prospective multi-center study involving over 160 adult patients showed a 40% relative increase in pneumonia cause identification when the Karius Spectrum test was used alongside standard care testing. In another retrospective study at Rady Children’s Hospital, the test led to a change in management for 78% of pediatric patients with complicated community-acquired pneumonia. The findings suggest that the Karius Spectrum test can enhance diagnostic accuracy and inform targeted therapy in pneumonia cases.