title: Evaluation of new laboratory tests to discriminate bacterial from nonbacterial chronic obstructive pulmonary disease exacerbations.
abstract: BACKGROUND
  Discriminating bacterial from nonbacterial acute exacerbations of chronic obstructive pulmonary disease (AECOPD) is difficult, causing antibiotics overuse and bacterial resistance. Sputum cultures are of limited use because results take time. In our hospital, only leukocyte concentration and CRP are laboratory parameters evaluated in AECOPD. We evaluated additional tests to discriminate bacterial vs. nonbacterial AECOPD: 5-part leukocyte differentiation (hematology analyzer), leukocyte differentiation using flow cytometry (Leukoflow, Cytodiff), Leuko64 kit, and procalcitonin.
  
  
  METHODS
  Retrospectively, patients were classified as bacterial or nonbacterial AECOPD. ROC analyses tested how the additional tests discriminate these groups.
  
  
  RESULTS
  Twenty-two AECOPD were classified as bacterial and 23 as nonbacterial. From the additional tests, basophil percentage (Cytodiff) has superior AUC (0.800). At a cutoff resulting in ≥90% sensitivity, neutrophil/lymphocyte ratio (AUC:0.755) and CD4-positive T cells (Leukoflow, AUC:0.747) have the highest specificity (57%). Both neutrophil mean volume and standard deviation (Cell Population Data, DxH800 hematology analyzer) had good combined sensitivity and specificity (AUC:0.846/0.804, 91% sensitivity, 69% specificity). Addition of leukocyte populations and procalcitonin to CRP in regression models (AUC: 0.907/0.876/0.890) increased specificity compared to CRP alone (71% or 73% vs. 39%).
  
  
  CONCLUSIONS
  No additional test has sufficient accuracy on its own to predict bacterial AECOPD. Combining CRP with several parameters from the additional tests may improve this.
authors.affiliation: Department of Clinical Chemistry (KCHL), Franciscus Gasthuis, Rotterdam, The Netherlands.
authors.forename: G-J M
authors.initials: GM
authors.lastname: van de Geijn
authors.affiliation: Department of Pulmonology/Internal Medicine, Franciscus Gasthuis, Rotterdam, The Netherlands.
authors.forename: S
authors.initials: S
authors.lastname: Denker
authors.affiliation: Department of Pulmonology/Internal Medicine, Franciscus Gasthuis, Rotterdam, The Netherlands.
authors.forename: V
authors.initials: V
authors.lastname: Meuleman-van Waning
authors.affiliation: Department of Microbiology, Franciscus Gasthuis, Rotterdam, The Netherlands.
authors.forename: H G M
authors.initials: HG
authors.lastname: Koeleman
authors.affiliation: Department of Statistics and Education, Franciscus Gasthuis, Rotterdam, The Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Birnie
authors.affiliation: Department of Pulmonology/Internal Medicine, Franciscus Gasthuis, Rotterdam, The Netherlands.
authors.forename: G-J
authors.initials: GJ
authors.lastname: Braunstahl
authors.affiliation: Department of Clinical Chemistry (KCHL), Franciscus Gasthuis, Rotterdam, The Netherlands.
authors.forename: T L
authors.initials: TL
authors.lastname: Njo
mesh_terms: D001424:Bacterial Infections / Q000175:diagnosis*; D001773:Blood Cells / Q000473:pathology; D002097:C-Reactive Protein / Q000032:analysis; D019411:Clinical Laboratory Techniques / Q000379:methods; D006801:Humans; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis*; D012372:ROC Curve; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D002097:C-Reactive Protein
keywords: Chronic obstructive pulmonary disease; bacterial infection; exacerbation; flow cytometry; leukocytes