title: Diagnostic accuracy of buffy coat culture compared to total blood culture in late-onset sepsis of the newborn.
abstract: OBJECTIVE
  To study the potential of buffy coat culture as a diagnostic tool for neonatal late-onset sepsis.
  
  
  METHODS
  This was a study of diagnostic accuracy in newborn infants born at 28-41 weeks of gestation, weighing >800g, with ≥8 points on the NOSEP-1 scale. Paired samples for total blood culture (TBC) and buffy coat culture were drawn. We established the positivity rate, sensitivity, specificity, predictive values, and likelihood ratios, and compared time to positivity and contamination rates.
  
  
  RESULTS
  Fifty-two newborns were included in the study. Twenty-one TBC and 22 buffy coat cultures were positive. The positivity rate for TBC was 40.4% and for buffy coat culture was 42.3% (p=not significant). Three TBC were positive with negative buffy coat culture. Four buffy coat cultures were positive with negative TBC; Kappa agreement was 0.723, p <0.001. Buffy coat culture sensitivity was 86% (95% confidence interval (CI) 68.5-95.4%), specificity 87% (75.4-93.7%), positive predictive value 82% (65.4-91.1%), negative predictive value 90% (77.9-96.8%), positive likelihood ratio 6.64 (2.79-15.05), and negative likelihood ratio 0.16 (0.05-0.42). We found no difference in time to positivity in hours; Wilcoxon Z=1224, p=0.22. The contamination rate was 1.9% for both methods.
  
  
  CONCLUSIONS
  Buffy coat culture is as good as TBC for the microbiological diagnosis of late-onset sepsis of the newborn. Buffy coat culture allows the use of remaining plasma for further analysis.
authors.affiliation: Tecnológico de Monterrey, Escuela de Medicina y Ciencias de la Salud, Programa Multicéntrico de Neonatología, ITESM y Cátedra de Terapia Celular, Ave. Ignacio Morones Prieto 3000 poniente, Edificio CITES, tercer piso, oficina 307, Col. Doctores, CP 64710, Monterrey, Nuevo León, Mexico. lara-diaz.vj@itesm.mx
authors.forename: Víctor Javier
authors.initials: VJ
authors.lastname: Lara-Díaz
authors.forename: Jessica
authors.initials: J
authors.lastname: De La Vega-Méndez
authors.forename: Víctor
authors.initials: V
authors.lastname: Arízaga-Ballesteros
authors.forename: Beatriz R
authors.initials: BR
authors.lastname: Tinoco-Torres
authors.forename: Jorge Eugenio
authors.initials: JE
authors.lastname: Moreno-Cuevas
mesh_terms: D001431:Bacteriological Techniques / Q000379:methods; D058621:Blood Buffy Coat / Q000382:microbiology*; D042241:Early Diagnosis; D005189:False Positive Reactions; D005260:Female; D005865:Gestational Age; D006801:Humans; D007231:Infant, Newborn; D016013:Likelihood Functions; D008297:Male; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D018805:Sepsis / Q000097:blood / Q000175:diagnosis*; D013997:Time Factors