Evaluation of a Direct-from-Blood Molecular Diagnostic Platform for Pathogen Detection in Critically Ill Patients: A Prospective Observational Cohort Study

Rationale: Defining the microbial etiology of sepsis is difficult but has important implications for antibiotic stewardship and prognosis. We explore the diagnostic yield of a novel, direct-from-blood multiplex polymerase chain reaction in intensive care unit patients with suspected sepsis. Methods: From March 2022 to March 2024, patients were included if the clinical team ordered a blood culture. In study participants, an additional 6 mL of whole blood was collected by the phlebotomist. Samples were analyzed by the RaPID/BSI platform, a polymerase chain reaction-based assay that detects 19 bacterial and fungal species direct from whole blood. Results: A total of 165 samples were included in the final cohort. Of these, 27 patients had a positive RaPID/BSI result and 8 patients had positive blood cultures with 1 pathogen not included in the RaPID/BSI panel. Of the 27 patients with positive RaPID/BSI results, 5 patients also had positive blood cultures. Pathogen identification from RaPID/BSI and blood cultures were concordant for 4 of 5 of these pathogens. Twenty-five of the 27 RaPID/BSI positive patients had clinically defined infections. Eighteen patients of the 27 RaPID/BSI-positive patients had additional positive microbial culture data that corroborated pathogen identification. Of the 27 patients with bloodstream infections detected by RaPID/BSI and/or blood cultures, 20 had received antibiotics in the 48 hours before their blood draw. The RaPID/BSI assay identified the pathogen in all 20 of these patients, whereas only 4 of these 20 patients had positive blood cultures. Conclusions: The diagnostic yield of a direct-from-blood molecular diagnostic assay for the detection of bloodstream infection was 15.2% compared to 4.3% from blood cultures, providing higher detection rate especially in the setting of recent antibiotic administration.