The white cell ratio in the very low birth weight infant

The purpose of this study was to assess the usefulness of the white cell ratio of immature neutrophils (PMNs) to total (immature plus mature) PMNs as an indication of infection in the very small premature infant. We retrospectively reviewed the charts of 59 premature infants less than or equal to 1,250 g admitted to our Newborn Intensive Care Unit over a one-year period who had at least one white count determined. Twenty-three were born after rupture of membranes for greater than or equal to 24 hours (PROM), 47 had a one-minute Apgar score less than or equal to 6 and 31 had a five-minute Apgar scores less than or equal to 6, 38 had respiratory distress syndrome (RDS), and 4 had confirmed infection. Thirty-one of the infants had a ratio greater than or equal to .15 in the first day of life, a value which has been suggested in the literature as being abnormal and an indication to suspect sepsis. This ratio bore no statistical relationship to PROM, low Apgar scores, or RDS. We analyzed these same relationships using a ratio greater than or equal to .25, another ratio derived from data in the literature which has been said to suggest infection. No statistical correlation was found for low Apgars or RDS, but there was a significant relationship between PROM and attainment of a ratio greater than or equal to .25 (p less than .005). It is notable that 2 out of the 4 infants with infection had a ratio less than .15. We wish to cast doubt on the applicability of the currently defined WBC ratios in the literature as they apply to the infant with birth weight less than 1,250 g and emphasize the apparent effect of PROM as a factor upon these ratios.