Plasma Neprilysin for Predicting Sepsis Within 48 Hours in ICU Patients With Infection or Suspected Infection

This is a multicenter prospective observational cohort study conducted in the intensive care units of Zhujiang Hospital, Southern Medical University, and Guangzhou First Municipal People's Hospital.

Newly admitted intensive care unit participants will be screened daily according to predefined eligibility criteria. Eligible participants with confirmed or suspected infection who do not meet the protocol-defined criteria for sepsis at enrollment will be approached consecutively. Written informed consent will be obtained from the participant or the participant's legally authorized representative before enrollment.

Day 0 is defined as the date of the first plasma sample collection. Plasma samples will be collected on Day 0 and Day 1, processed according to standardized procedures, aliquoted, stored at -80 degrees Celsius, and batch-tested for neprilysin, interleukin-6, C-reactive protein, and procalcitonin. Laboratory personnel will be blinded to clinical outcomes.

When oral conditions permit, sublingual microcirculation will be assessed on Day 0 and Day 1. Measurements will include microvascular flow index, perfused vessel density, and perfused boundary region. Image assessors will be blinded to clinical outcomes.

Sequential Organ Failure Assessment 2 scores will be evaluated at baseline, Day 1, and Day 2. Development of sepsis within 48 hours will be independently adjudicated by two investigators who are blinded to plasma neprilysin and sublingual microcirculation results. Disagreements will be resolved by a senior intensive care physician.

Receiver operating characteristic curve analysis and logistic regression will be used to evaluate plasma neprilysin alone and in combination with conventional biomarkers and sublingual microcirculation measurements. Predictive performance will be internally validated using bootstrap resampling.

Inclusion criteria

• Age 18 years or older.
• Confirmed or suspected infection as assessed by the treating physician based on symptoms, signs, laboratory findings, imaging findings, microbiological findings, or evidence of an infection source, with systemic antimicrobial therapy initiated or planned.
• Does not meet the protocol-defined criteria for sepsis at enrollment. In the setting of confirmed or suspected infection, there must be no acute increase of 2 or more points in the Sequential Organ Failure Assessment 2 score from baseline that is attributable to infection.
• Expected by the treating physician to remain in the intensive care unit for more than 48 hours after enrollment.
• Written informed consent provided by the participant or the participant's legally authorized representative.

Exclusion criteria

• Sepsis diagnosed at intensive care unit admission or fulfillment of the Sepsis-3 criteria at screening.
• Insufficient clinical data to determine the baseline SOFA-2 score according to the prespecified assessment criteria.
• Patients with limited nursing care (patients for whom active treatment has been withdrawn)
• No blood sample is available on the day of enrollment.
• Considered unsuitable for participation by the investigator.