title: Nucleated red blood cells in term fetuses: reference values using an automated analyzer.
abstract: BACKGROUND
  Nucleated red blood cells (NRBCs) are present in small numbers in the cord blood of healthy fetuses at birth. Acute and chronic stimuli, such as fetal hypoxia, cause increased circulating levels of NRBCs. Manual counting is presently the only way to quantify NRBCs, but it is time-consuming and inaccurate. Recently, automated approaches have been developed in order to quantify NRBCs.
  
  
  OBJECTIVE
  Our aim was to compare manual vs. automated NRBC counting and derive reference values in umbilical cord blood samples from healthy term fetuses.
  
  
  METHODS
  We analyzed blood samples from 131 healthy term fetuses by the automated approach and calculated reference values of NRBC counts as percentiles. To compare automated NRBC count with manual count we obtained umbilical cord blood samples from 50 further fetuses.
  
  
  RESULTS
  Significant positive correlation was obtained between the two methods (r(2) = 0.988, Bland-Altman plot mean difference NRBCs/100 WBC: -0.590). The median for NRBCs/100 WBC was 3.05 (range 0-11.6) and the median for absolute NRBC counts x10(9)/l was 0.39 (range 0-1.8).
  
  
  CONCLUSIONS
  We demonstrate that values obtained with the automated NRBC counting method are comparable to those obtained with the microscopic manual evaluation and give reference values for umbilical cord NRBCs at term that can be used in clinical practice.
authors.affiliation: Department of Obstetrics and Gynecology, University of Turin, Turin, Italy. alessandro.rolfo@unito.it
authors.forename: Alessandro
authors.initials: A
authors.lastname: Rolfo
authors.forename: Mariacaterina
authors.initials: M
authors.lastname: Maconi
authors.forename: Simona
authors.initials: S
authors.lastname: Cardaropoli
authors.forename: Marilisa
authors.initials: M
authors.lastname: Biolcati
authors.forename: Paolo
authors.initials: P
authors.lastname: Danise
authors.forename: Tullia
authors.initials: T
authors.lastname: Todros
mesh_terms: D000328:Adult; D001322:Autoanalysis / Q000295:instrumentation* / Q000379:methods; D001724:Birth Weight; D004900:Erythroblasts / Q000166:cytology*; D004906:Erythrocyte Count / Q000295:instrumentation* / Q000379:methods; D005260:Female; D005312:Fetal Blood / Q000166:cytology*; D005865:Gestational Age; D006801:Humans; D008297:Male; D011446:Prospective Studies; D012016:Reference Values; D015203:Reproducibility of Results; D047929:Term Birth / Q000097:blood*