Objective: CD64 index and triggering receptor expressed on myeloid cells-1 are biomarkers on neutrophil polymorphonuclear cells with crucial role in sepsis. The study aim is to assess diagnostic performance, individually and combined, of CD64 index and triggering receptor expressed on myeloid cells-1 (surface marker/soluble form), in late-onset sepsis of preterm infants.
Design: Observational study.
Setting: Neonatal ICU.
Patients: Sixteen septic and 16 control preterm infants, gestational age younger than 32 weeks and/or birth weigh less than 1500 g.
Measurement and main results: Seventy preterm infants, free of sepsis were enrolled into the study. CD64 index and triggering receptor expressed on myeloid cells-1 were measured once between day 5 and 15 of life (T0) and once between day 16 and 25 (T1). At T1, 16 infants were assigned to septic group because of reported signs of sepsis and positive blood culture. From the remaining 54 infants, 16 of them who always remained free of sepsis had a blood sample at T1 and constituted the control group (n = 16). Comparing T1 vs T0, triggering receptor expressed on myeloid cells-1 polymorphonuclear cells percentage was significantly lower (p = 0.002) in septic group but not in control group; soluble triggering receptor expressed on myeloid cells-1 concentration did not show significant differences in both groups; CD64 index significantly increased (p = 0.0004) in septic group, while no difference was found in control group. Comparing septic with control group at T0, no differences were found in any markers. At T1, triggering receptor expressed on myeloid cells-1 polymorphonuclear cells percentage was significantly lower (p = 0.003) and CD64 index was higher (p = 0.00019) in septic infants. Triggering receptor expressed on myeloid cells-1 polymorphonuclear cells receiver operating characteristic curve indicated cutoff 62.12%, sensitivity 56.2%, specificity 93.5%, and area under the curve 0.8. CD64 index receiver operating characteristic curve indicated cutoff 2.85, sensitivity 87.5%, specificity 100%, and area under the curve 0.95. Combination of the two indexes was not useful in increasing individual diagnostic power.
Conclusions: Despite limited sample size, CD64 index demonstrated to be a promising biomarker, with high specificity, to diagnose late-onset sepsis. Further investigations are needed to substantiate these findings. Triggering receptor expressed on myeloid cells-1 showed less valuable diagnostic role.