253 Interleukin-6 and C Reactive Protein in Serum and Urine of Neonates

Abstract

Background: Interleukin-6 (IL-6) and C reactive protein (CRP) are frequently detectable in amniotic fluid (AF). While CRP seems to be excreted by the fetal kidneys and probably by the lungs, IL-6 is an inflammatory cytokine produced by activated macrophages and lymphocytes which gain access to the amniotic cavity during intrauterine infection. IL-6 and other proinflammatory cytokines are also found in bronchoalveolar lavage of ventilated infants and in the urine of children with urinary tract infection. However, no information is available on the urinary IL-6 (uIL-6) content of neonates. Methods: Urine and blood samples were obtained from consecutive neonates in the first week of life. Urine was collected using sterile cotton flock. After centrifugation of the flock, urinary CRP (uCRP) was put in sterile tubes and sent immediately to the laboratory. Urinary CRP and uIL-6 were measured with a commercially available ELISA test. The sensitivity of the assay was below 10% for both measurements. The uCRP and uIL-6 values were normalized for the urinary creatinine content of every single probe. Spearman rank correlation was used for statistical purposes. Results: Serum and urinary CRP and IL-6 were measured in 15 infants. Mean±SD gestational age at delivery and birth weight were 33.3±3.8 weeks and 1789±794 grams, respectively. Serum and uCRP was detectable in all samples with a median (range) serum concentration of 2830.2 ng/mL (113.3–187171) and 4.76 ng/mL (0.83–58.73) in the urine. No correlation was found between serum CRP and uCRP concentration. IL-6 was present in 14 (93.3%) blood samples and in 9 (60%) urine samples. The median (range) concentration of IL-6 was 3.6 pg/ml (0–542.5) in serum and 0.48 pg/ml (0–39.5) in urine, respectively. A significant correlation was found between serum IL-6 and uIL-6 (r=0.56; p<0.05). No correlation was found between uCRP and IL-6 in serum and urine. Conclusion: IL-6 can be present in neonatal urine at birth. This suggests that fetal urine could be another source of amniotic fluid IL-6 during intrauterine inflammatory processes.