Nucleated red blood cells as marker for an increased risk of unfavorable outcome and mortality in very low birth weight infants.

Background: Nucleated red blood cells (NRBC) are normoblastic cells that failed to extrude their nuclei before exiting from bone marrow or liver. While NRBC are frequently found in umbilical cord blood after fetal distress, NRBC counts drop rapidly after birth.

Aims: To determine the predictive value of the NRBC count during the first 120h after birth as marker for later risk of unfavorable outcome in very preterm infants.

Study Design: This cohort study investigated the association between absolute count of NRBC on admission (day 1), the mean NRBC count between day 2 to 5, and outcome (mortality or the composite outcome of mortality and severe morbidity).

Results: 438 infants with a gestational age<32weeks and a birth weight<1500g were included within a five-year period, of whom 46 patients died and 65 suffered from severe morbidity. Nonsurvivors had significantly higher NRBC counts between day 2 and 5, as compared to survivors. This finding was observed in infants both appropriate and small for gestational age. An increase of 10/nL of the mean NRBC count on postnatal day 2 to 5 had an odds ratio for mortality of 6.95 (95% CI 2.21-21.86) and an odds ratio for the composite outcome mortality and severe morbidity of 3.43 (95% CI 1.43-8.24). The optimal cut-off value for prediction of death was NRBC >2/nL with a sensitivity of 85% and a specificity of 75%.

Conclusions: Elevation of NRBC on postnatal day 2 to 5 is an independent predictor of mortality in preterm infants.