title: Procalcitonin (PCT) levels for ruling-out bacterial coinfection in ICU patients with influenza: A CHAID decision-tree analysis.
abstract: OBJECTIVE
  To define which variables upon ICU admission could be related to the presence of coinfection using CHAID (Chi-squared Automatic Interaction Detection) analysis.
  
  
  METHODS
  A secondary analysis from a prospective, multicentre, observational study (2009-2014) in ICU patients with confirmed A(H1N1)pdm09 infection. We assessed the potential of biomarkers and clinical variables upon admission to the ICU for coinfection diagnosis using CHAID analysis. Performance of cut-off points obtained was determined on the basis of the binominal distributions of the true (+) and true (-) results.
  
  
  RESULTS
  Of the 972 patients included, 196 (20.3%) had coinfection. Procalcitonin (PCT; ng/mL 2.4 vs. 0.5, p < 0.001), but not C-reactive protein (CRP; mg/dL 25 vs. 38.5; p = 0.62) was higher in patients with coinfection. In CHAID analyses, PCT was the most important variable for coinfection. PCT <0.29 ng/mL showed high sensitivity (Se = 88.2%), low Sp (33.2%) and high negative predictive value (NPV = 91.9%). The absence of shock improved classification capacity. Thus, for PCT <0.29 ng/mL, the Se was 84%, the Sp 43% and an NPV of 94% with a post-test probability of coinfection of only 6%.
  
  
  CONCLUSIONS
  PCT has a high negative predictive value (94%) and lower PCT levels seems to be a good tool for excluding coinfection, particularly for patients without shock.
authors.affiliation: Critical Care Department, Hospital Universitari de Tarragona Joan XXIII, IISPV/URV/CIBERes, Tarragona, Spain. Electronic address: ahr1161@yahoo.es.
authors.forename: Alejandro H
authors.initials: AH
authors.lastname: Rodríguez
authors.affiliation: Otorhinolaryngology Head-Neck Surgery Department, Hospital Universitari de Tarragona Joan XXIII, IISPV/URV, Tarragona, Catalonia, Spain. Electronic address: fxavilesj@gmail.com.
authors.forename: Francesc X
authors.initials: FX
authors.lastname: Avilés-Jurado
authors.affiliation: Critical Care Department, ParcTaulí Hospital/CIBERes, Sabadell, Spain. Electronic address: emilio.diaz.santos@gmail.com.
authors.forename: Emili
authors.initials: E
authors.lastname: Díaz
authors.affiliation: Internal Medicine Department, Kantonsspital Aarau, Switzerland. Electronic address: schuetzph@gmail.com.
authors.forename: Philipp
authors.initials: P
authors.lastname: Schuetz
authors.affiliation: Critical Care Department, Hospital Universitari de Tarragona Joan XXIII, IISPV/URV/CIBERes, Tarragona, Spain. Electronic address: sitrefler@yahoo.es.
authors.forename: Sandra I
authors.initials: SI
authors.lastname: Trefler
authors.affiliation: Critical Care Department, Hospital Dr. Negrín, Las Palmas de Gran Canaria, Spain. Electronic address: jsolvio@gobiernodecanarias.org.
authors.forename: Jordi
authors.initials: J
authors.lastname: Solé-Violán
authors.affiliation: Critical Care Department, CHUAC, A Coruña, Spain. Electronic address: lcorlor@gmail.com.
authors.forename: Lourdes
authors.initials: L
authors.lastname: Cordero
authors.affiliation: Critical Care Department, Hospital de Donostia, San Sebastian, Spain. Electronic address: loreto.vidaurtello@osakidetza.net.
authors.forename: Loreto
authors.initials: L
authors.lastname: Vidaur
authors.affiliation: Critical Care Department, Hospital SAS, Jerez de la Frontera, Spain. Electronic address: litoestella@hotmail.com.
authors.forename: Ángel
authors.initials: Á
authors.lastname: Estella
authors.affiliation: Critical Care Department, Hospital Reina Sofía, Córdoba, Spain. Electronic address: juanc.pozo.sspa@juntadeandalucia.es.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Pozo Laderas
authors.affiliation: Critical Care Department, Hospital Son Llatzer, Palma de Mallorca, Spain. Electronic address: lsocias3@gmail.com.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Socias
authors.affiliation: Critical Care Department, Hospital de Cruces, Vizcaya, Spain. Electronic address: juancarlos.vergaraserrano@osakidetza.net.
authors.forename: Juan C
authors.initials: JC
authors.lastname: Vergara
authors.affiliation: Critical Care Department, Hospital Dr. Peset, Valencia, Spain. Electronic address: zaragozar@ono.com.
authors.forename: Rafael
authors.initials: R
authors.lastname: Zaragoza
authors.affiliation: Critical Care Department, Hospital La Fe, Valencia, Spain. Electronic address: bonastre_jua@gva.es.
authors.forename: Juan
authors.initials: J
authors.lastname: Bonastre
authors.affiliation: Critical Care Department, Hospital Gregorio Marañón, Madrid, Spain. Electronic address: jeguerrerosanz@gmail.com.
authors.forename: José E
authors.initials: JE
authors.lastname: Guerrero
authors.affiliation: Critical Care Department, Hospital Universitario de Santander, Spain. Electronic address: borja.suberviola@gmail.com.
authors.forename: Borja
authors.initials: B
authors.lastname: Suberviola
authors.affiliation: Critical Care Department, Hospital Clinic / CIBERES, Barcelona, Spain. Electronic address: catiacilloniz@yahoo.com.
authors.forename: Catia
authors.initials: C
authors.lastname: Cilloniz
authors.affiliation: Division of Pulmonary Diseases and Critical Care Medicine, University of Texas Health Science Center at San Antonio San Antonio, TX, USA. Electronic address: restrepom@uthscsa.edu.
authors.forename: Marcos I
authors.initials: MI
authors.lastname: Restrepo
authors.affiliation: Multidisciplinary Intensive Care Research Organization (MICRO), Department of Anaesthesia and Critical Care, St James's University Hospital, Trinity Centre for Health Sciences, Dublin, Ireland. Electronic address: drmartinloeches@gmail.com.
authors.forename: Ignacio
authors.initials: I
authors.lastname: Martín-Loeches
mesh_terms: D000328:Adult; D001424:Bacterial Infections / Q000175:diagnosis* / Q000473:pathology*; D015415:Biomarkers / Q000097:blood; D002116:Calcitonin / Q000097:blood*; D015740:Calcitonin Gene-Related Peptide; D060085:Coinfection / Q000175:diagnosis* / Q000473:pathology*; D003663:Decision Trees; D005260:Female; D006801:Humans; D007251:Influenza, Human / Q000150:complications* / Q000473:pathology*; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011446:Prospective Studies; D011498:Protein Precursors / Q000097:blood*; D012680:Sensitivity and Specificity
chemical_list: D015415:Biomarkers; C000606589:CALCA protein, human; D011498:Protein Precursors; D002116:Calcitonin; D015740:Calcitonin Gene-Related Peptide
keywords: CHAID analysis; Community-acquired pneumonia; Influenza A(H1N1)pmd; Procalcitonin; Prognosis; Respiratory coinfection; Septic shock