Urinary immune biomarkers for late-onset sepsis in preterm very low birth weight neonates - a diagnostic accuracy study.

Objectives: To evaluate diagnostic accuracy of urinary immune biomarkers (IBM) for late-onset sepsis (LOS) in very preterm infants.

Methods: This multicenter, prospective diagnostic accuracy study, included preterm infants <32 weeks of gestation and birth weight <1,500 g, needing evaluation for suspected LOS. Urine samples obtained concurrent to blood culture and sepsis screen were evaluated for interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) levels using enzyme immunoassay. Positive blood and/or CSF culture served as reference standards. Receiver operating characteristic curves were used to evaluate performance of urinary IBM for detection of LOS.

Results: During September 2021-September 2023, we evaluated 136 preterm, very low birth weight infants (mean gestational age: 28.2 weeks, mean birth weight: 933 g) for sepsis after 72 h of postnatal age and prior to 37 weeks postmenstrual age. Twenty four infants had culture-positive sepsis. Median IL-8 and MCP-1 levels in neonates with LOS were 86.5 pg/mL and 230.2 pg/mL and those in non-infected neonates were 66.5 pg/mL and 212.1 pg/mL. Urinary IL-8 had sensitivity and specificity of 42 and 51 % [AUC: 0.46 (0.35-0.57)] and urinary MCP-1 had sensitivity and specificity of 46 and 53 % [AUC: 0.49 (0.38-0.60)] for detection of LOS.

Conclusions: Urinary IL-8 and MCP-1 had low sensitivity and specificity for diagnosis of LOS in very preterm infants. These findings underscore the need to establish reference ranges for urinary IBM in preterm neonates.