title: Longitudinal analysis of leukocyte differentials in peripheral blood of patients with acute respiratory viral infections.
abstract: BACKGROUND
  Leukocyte counts and differentials are commonly acquired in patients with suspected respiratory viral infections and may contribute diagnostic information. However, most published work is limited to a single timepoint at initial presentation to a medical provider, which may correspond to widely varying points in the course of disease.
  
  
  OBJECTIVE
  To examine the temporal development and time-dependent utility of routine leukocyte differentials in the diagnosis of respiratory viral infections.
  
  
  METHODS
  We analyzed data from recent experimental human challenges with influenza A/H3N2, human rhinovirus (HRV), and respiratory syncytial virus (RSV). Routine clinical lab cell counts and differentials were measured daily from the time period immediately prior to inoculation through the eventual resolution of symptomatic disease.
  
  
  RESULTS
  Approximately 50% of challenged individuals developed symptoms and viral shedding consistent with clinical disease. Subpopulations of WBC showed marked differences between symptomatic and asymptomatic individuals over time, but these changes were much more profound and consistent in influenza infection. Influenza-infected subjects develop both relative lymphopenia and relative monocytosis, both of which closely mirror symptom development in time. A lymphocyte:monocyte ratio of <2 correctly classifies 100% of influenza (but not RSV or HRV) infected subjects at the time of maximal symptoms.
  
  
  CONCLUSIONS
  Leukocyte differentials may suggest a viral etiology in patients with upper respiratory infection, but are not sufficient to allow differentiation between common viruses. Timing of data acquisition relative to the disease course is a key component in determining the utility of these tests.
authors.affiliation: Durham VA Medical Center, Durham, NC, United States; Division of Infectious Diseases, Duke University Medical Center, Durham, NC, United States. Electronic address: micah.mcclain@duke.edu.
authors.forename: Micah T
authors.initials: MT
authors.lastname: McClain
authors.forename: Lawrence P
authors.initials: LP
authors.lastname: Park
authors.forename: Bradly
authors.initials: B
authors.lastname: Nicholson
authors.forename: Timothy
authors.initials: T
authors.lastname: Veldman
authors.forename: Aimee K
authors.initials: AK
authors.lastname: Zaas
authors.forename: Ron
authors.initials: R
authors.lastname: Turner
authors.forename: Robert
authors.initials: R
authors.lastname: Lambkin-Williams
authors.forename: Anthony S
authors.initials: AS
authors.lastname: Gilbert
authors.forename: Geoffrey S
authors.initials: GS
authors.lastname: Ginsburg
authors.forename: Christopher W
authors.initials: CW
authors.lastname: Woods
mesh_terms: D000328:Adult; D015331:Cohort Studies; D005260:Female; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype / Q000302:isolation & purification; D007251:Influenza, Human / Q000097:blood / Q000276:immunology / Q000821:virology; D007958:Leukocyte Count; D007962:Leukocytes / Q000166:cytology*; D008137:Longitudinal Studies; D008297:Male; D010850:Picornaviridae Infections / Q000097:blood / Q000276:immunology / Q000821:virology; D012372:ROC Curve; D018357:Respiratory Syncytial Virus Infections / Q000097:blood / Q000276:immunology / Q000821:virology; D012136:Respiratory Syncytial Viruses / Q000302:isolation & purification; D012141:Respiratory Tract Infections / Q000097:blood* / Q000276:immunology / Q000821:virology; D012229:Rhinovirus / Q000302:isolation & purification; D055815:Young Adult
keywords: Clinical testing; Influenza; Respiratory virus