Admission red cell distribution width-to-albumin ratio and risk of neonatal pneumonia or culture-proven sepsis in preterm infants: a retrospective cohort study.

BACKGROUND

Red cell distribution width-to-albumin ratio (RAR), a biomarker reflecting inflammation and nutritional status, may be associated with adverse neonatal outcomes. Given that neonatal infection remains a major complication in preterm infants, this study aimed to evaluate the association between admission RAR and the risk of subsequent neonatal infection, and to explore potential non-linear patterns.

METHODS

This retrospective cohort included 697 preterm infants (24⁰⁄₇-36⁶⁄₇ weeks) admitted to a tertiary NICU (2019-2024). RAR was calculated from RDW and albumin measured within 2 h of admission. The primary outcome was a subsequent composite neonatal infection during the NICU stay, defined as neonatal pneumonia and/or culture-proven sepsis. Multivariable logistic regression analyzed RAR continuously and by quartiles; restricted cubic splines and two-piecewise regression assessed non-linearity.

RESULTS

Infants in higher RAR quartiles had lower gestational age and a higher incidence of subsequent composite neonatal infection. When analyzed as a continuous variable, RAR was not significantly associated with overall neonatal infection. However, in quartile analyses, higher RAR levels were independently associated with an increased risk of subsequent neonatal pneumonia, which accounted for the majority of infection events. No significant association was observed for culture-proven sepsis. A significant non-linear relationship between RAR and pneumonia risk was identified, with an apparent inflection point at 5.65 identified in exploratory restricted cubic spline analyses. Sensitivity analyses yielded consistent results.

CONCLUSION

Admission RAR was non-linearly associated with the risk of subsequent neonatal pneumonia in preterm infants, with an apparent inflection point at 5.65 identified in exploratory analyses. Although RAR may serve as a complementary marker for risk stratification, its performance was comparable to albumin alone without evidence of superiority over established inflammatory markers. Further prospective studies are needed to confirm these results.