Evaluation of IL-8-Concentrations in Plasma and Lysed EDTA-Blood in Healthy Neonates and Those with Suspected Early Onset Bacterial Infection

Abstract

Plasma IL-8 is a diagnostic parameter of early-onset bacterial infection (EOBI) in neonates but has a short half-life. The detergent-lysed whole-blood (DLWB) IL-8 consists of both extracellular and cell-bound IL-8. The objective of this study was to investigate kinetics of plasma and DLWB IL-8 in healthy newborns and those with suspected EOBI and to test the hypothesis that determination of DLWB IL-8 results in higher sensitivity for EOBI detection. Sixty-one neonates with clinical and serologic signs of EOBI composed the study group; 188 neonates with risk factors but without EOBI served as control subjects. IL-8 concentrations were determined in plasma and DLWB. In the control group, DLWB IL-8 concentrations were 280-fold higher (9599 pg/mL; SD 4433) up to 24 h post partum than corresponding plasma levels (34.2 pg/mL; SD 18.1). The sensitivity of DLWB versus plasma IL-8 for EOBI was 0.97 versus 0.71 after 6 h and 0.70 versus 0.32 after 24 h. Corresponding values for specificity were 0.95 versus 0.90 after 6 h and 0.92 versus 0.99 after 24 h. After 24 h, the negative predictive value for DLWB versus plasma IL-8 was 0.80 versus 0.66. DLWB IL-8 showed a higher sensitivity for EOBI within 6 h after first clinical suspicion than plasma IL-8. It also remained elevated longer. Our results suggest that DLWB IL-8 results in a higher sensitivity for EOBI. Abbreviations CRP, C-reactive protein DLWB, detergent-lysed whole blood EOBI, early-onset bacterial infection I/T ratio, immature to total neutrophil ratio NPV, negative predictive value PPV, positive predictive value ROC, receiver operator characteristics Neonates are susceptible to infections (1). The differential diagnosis of early-onset bacterial infection (EOBI) therefore must always be present for the neonatologist, regardless of how minor, unexpected, or discrete the clinical symptoms. EOBI is usually defined as occurring up to 72 h after birth (2) and is associated with a high morbidity and mortality risk (1). The nonspecific clinical signs as well as the currently established biochemical and hematologic parameters have their diagnostic limitations (3,4) [reviewed in (5,6)].Plasma IL-8 is an appreciated, highly predictive, and easily accessible chemokine to detect EOBI (7). IL-8 secretion is not limited to infections (8 -10), yet it occurs within 1-3 h of endotoxin challenge (11). As with most cytokines, its plasma half-life is short (Ͻ4 h) (12,13). Circulating IL-8, which can be detected in plasma or serum via immunoassay, is immediately bound to two distinct high-affinity IL-8 receptors that are abundantly present on neutrophils before internalization and degradation (14,15). Therefore, plasma IL-8 reflects only a small portion of the total IL-8 blood pool, because the majority is cell associated (16 -18).Cell association is enhanced by chemokine binding, non-IL-8 -specific receptors. These have been identified on various cell types (19), including the Duffy antigen-related chemokine receptors (16), presented on erythrocytes. Duffy antigenrelated chemokine-li...

A novel B-RAF inhibitor blocks interleukin-8 (IL-8) synthesis in human melanoma xenografts, revealing IL-8 as a potential pharmacodynamic biomarker

“…Thus, mice with WM-266-4 xenograft tumors at an average volume of 500 mm 3 received s.c. administration of compound 1 at 30 mg/kg over a 12-h period such that plasma drug levels would be >1 Amol/L (12 h was chosen due to the long half-life of plasma IL-8 as deduced from ref. 28). Further, s.c. administration was the preferred route of dosing as compound 1 had poor oral bioavailability.…”

Lipopolysaccharide-binding protein in noninfected neonates and those with suspected early-onset bacterial infection

“…In all, 32 neonates in the noninfected group and 12 in the suspected EOBI group also participated in an investigation on lysed whole blood interleukin-8 (IL-8). 4 Blood was collected from neonates who underwent blood testing because of risk factors for EOBI, but had no clinical signs or subsequent laboratory changes (noninfected group). To exclude EOBI, blood was drawn up to three times per patient at 6-12, 12-24 and 24-72 h post partum in addition to close observation by experienced neonatologists at least three times per day.…”

“…Clinical signs were fever (X37.81C rectal), hypothermia (p36.51C), temperature instability (X1.51C), pallor, grayish skin colour, poor perfusion (capillary refill >2 s), tachypnea (>60 respirations per minute at rest), dyspnea (grunting, nasal flaring, retractions), respiratory insufficiency, apnea, rising FiO 2 in previously stable neonates, arterial hypotension (mean arterial blood pressure <37 mmHg), muscular hypotonia, irritability, hyperexcitability, neck stiffness, and lethargy. 4,15 The CRP cutoff of 10 mg/l has been used in our institution for many years according to previous investigations. 4,15,16 Workup program for suspected EOBI Indications for close clinical observation and our blood screening program were one or a combination of the following criteria: history of amniotic infection, maternal leukocytosis (>12 000 leukocytes/mm 3 ), and/or maternal CRP elevation to >10 mg/l after exclusion of infectious foci unrelated to the fetus (gastrointestinal or urinary tract infections), fetal tachycardia (>160 beats/min), prolonged rupture of membranes (X12 h) in the absence of labour, maternal fever (rectal temperature X38.01C), and foul smelling amniotic fluid.…”

“…in 1), since C-reactive protein (CRP) has a limited sensitivity in the early phase 1,2 and proinflammatory plasma cytokines generally decrease to normal values within hours, 3 potentially leaving a diagnostic gap between cytokine decrease and CRP increase. 4 Lipopolysaccharide-binding protein (LBP) is an acute-phase protein produced mainly by hepatocytes. 5 It transforms lipopolysaccharide (LPS) and facilitates interaction with monocyte membrane CD14.…”

Serum amyloid A: an early and accurate marker of neonatal early-onset sepsis

“…However, most studies investigating this early marker of neonatal EOS concluded that procalcitonin is not better than CRP in assessing EOS and that its diagnostic accuracy is complicated by a physiological increase during the first days of life. 4 Several studies, analyzing term infants suspected of sepsis, have recently shown that inflammatory markers such as whole-blood IL-8 and neutrophil CD64 are very sensitive indicators of EOS in a research setting, [5][6] yet because of special handling requirements, they are not readily available in hospital laboratories.…”