Host-based Immunoassay for Differentiating Bacterial From Viral Infections (Post-marketing Study of ImmunoXpert™ - SPIRIT Study)

This is a retrospective external field study of a novel in vitro diagnostic (IVD) assay (ImmunoXpert™). The study will involve reviewing the medical charts of about 4500 pediatric patients that were tested using ImmunoXpert™ as part of the routine workup for acute febrile illness. ImmunoXpert™ uses a computer algorithm to combine immunoassay measurements of three host immune proteins (TRAIL, IP-10, and CRP) present in human blood. The test is intended for use in conjunction with clinical assessments and other laboratory findings as an aid to differentiate bacterial from viral infection. Statistical analysis will be performed to compare the diagnostic accuracy of ImmunoXpert™ with that of current practice lab testing e.g., WBC, CRP, and PCT (whichever were taken as part of routine care) and clinical suspicion at time of requisition.