OBJECTIVE: To assess the value of serum levels of soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) for early diagnosis of late-onset sepsis (LOS) in neonates, compared with interleukin-6 (IL-6).DESIGN AND SETTING: Prospective, observational study in a single, level III neonatal intensive care unit of a university hospital.PATIENTS: Fifty-two preterm and term neonates evaluated for suspected LOS were studied. Neonates were classified into two groups: infected [confirmed sepsis (n = 22) and possible sepsis (n = 9)] and noninfected neonates (n = 21).MEASUREMENTS AND RESULTS: Serum sTREM-1 and IL-6 were measured (enzyme-linked immunosorbent assays) when signs suggestive of sepsis emerged. Infected neonates had significantly higher sTREM-1 (p = 0.004) and IL-6 (p < 0.0001) than noninfected neonates. Receiver operating characteristic (ROC) curve analysis resulted in significant areas under the curve (AUC) for both sTREM-1 (AUC = 0.733, p = 0.005) and IL-6 (AUC = 0.892, p = 0.001) for identification of infected neonates, with the difference between the two AUC not being significant. Further analysis documented acceptable diagnostic performance of sTREM-1 and IL-6, which was not improved, however, when the two markers were combined.CONCLUSIONS: Serum sTREM-1 increases in infected neonates. Diagnostic accuracy of sTREM-1 either alone or in combination with IL-6 is not better than that of IL-6.