This study is a proteomics-based diagnostic biomarker study conducted on the same patient cohort as the transcriptomic biomarker study (NCT065529754). Although both studies share the same clinical cohort and overarching diagnostic aim, they are registered separately because they employ distinct omics technologies, investigate different biomarker modalities, and yield independent outcome measures.

This study aims to identify and validate proteomics-based diagnostic biomarkers for differentiating bacterial from viral acute febrile illnesses. It is conducted on the same patient cohort previously used in a registered transcriptomic biomarker study (ClinicalTrials.gov Identifier: NCT065529754).

Although both studies share the overarching clinical objective of improving infection triage, they are scientifically independent in terms of methodology, biomarker modality, and analytical pipeline. Transcriptomic study (NCT065529754): Focused on host-response gene expression signatures derived from RNA sequencing data. Proteomic study (this registration): Focuses on host-response protein biomarkers identified through high-resolution mass spectrometry (DIA/PRM/SRM) and validated by immunoassays (ELISA).

The proteomics study is designed to discover a minimal and biologically distinct set of protein markers that can be readily translated into clinical diagnostics. This study evaluates a minimal set of circulating proteins-ICAM1, CFHR5, and GRN-discovered through AI-assisted proteomics and validated by ELISA, as a rapid diagnostic tool for bacterial vs viral infection. Patients with acute fever are prospectively enrolled into three cohorts: discovery, internal validation, and external validation.

This independent registration reflects the proteomics-specific objectives, methodology, and outcomes, while also acknowledging its linkage to the transcriptomics study.

Inclusion Criteria:

• Age ≥14 years；
• Body temperature > 38°C(within the past 72 hours)；
• Disease duration ≤ 14 days；
• Provision of informed consent by patient or legal guardian.

Exclusion Criteria:

• Underlying diseases affecting immune function (e.g., advanced malignancy, autoimmune disease, immunodeficiency, use of immunosuppressants);
• Pregnancy;
• Mixed infections (including viral-bacterial co-infections, bacterial or viral-fungal co-infections, or autoimmune disease concomitant with bacterial infection);
• indeterminate or negative microbiological testing ;
• inability to provide informed consent

Patients aged 14 years or older who presented to the emergency department with acute febrile illness (fever ≤14 days, ≥38°C within 72 hours) and suspected bacterial or viral infection.

De-identified individual participant-level clinical data and proteomic assay data generated from plasma samples will be shared.

Available after publication of primary results.

Researchers with approved proposals and signed data-sharing agreements.