CIRCULATING NEUTROPHILS IN SEPTIC PRETERM NEONATES - COMPARISON OF 2 REFERENCE RANGES

Objective. To study the effect of sepsis on circulating neutrophils in very low birth weight neonates and to assess the usefulness of recent ly revised reference ranges for circulating neutrophils in the diagnos is of sepsis in this population by comparison with previously reported reference ranges. Methods. Neutrophil parameters (absolute total neut rophils, absolute total immature neutrophils, and the immature:total n eutrophil proportion) were analyzed retrospectively in 202 sepsis epis odes in 192 neonates (birth weight = 1055 +/- 246 g, X +/- SD; estimat ed gestational age = 29 +/- 2 weeks) between birth and 30 days of age. The percentage of values lying outside the reference ranges reported recently by Mouzinho et al(32) and previously by Manroe et al(24) were compared. To more accurately assess possible differences in specifici ty between the two reference ranges, neonates with early-onset group B streptococcal infection (n = 19) were compared with a matched control group (n = 51) using conditional logistic regression. Results. Greate r sensitivity was observed using the previous reference ranges of Manr oe et al(24) over the entire study period (0 to 720 hours) both for th e initial and the second complete blood count (CBC). The previous refe rence ranges also were more sensitive than the revised ranges for the initial CBC at 0 to 72 and at 73 to 720 hours and for infections attri butable to coagulase-negative staphylococci. However, specificity in n eonates without group B streptococcal infection was significantly grea ter with the revised reference ranges compared with those of Manroe et al(24) (initial CBC, 73% vs 45%; serial CBCs, 59% vs 10%). Conclusion . The observed differences in sensitivities may be of limited clinical significance because very low birth weight infants often are begun on antibiotic therapy regardless of laboratory values. However, the stri king differences in specificity using the revised reference ranges sug gest that these ranges may be clinically useful in determining length of antimicrobial therapy in infants in whom cultures remain sterile.