title: Diagnosis of influenza: only a problem of coding?
abstract: OBJECTIVE
  To evaluate the characteristics of hospital discharge diagnoses of influenza measured by using specific International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9 CM) codes.
  
  
  METHODS
  The study was conducted for the 3 years 2007, 2008 and 2011. The database included (1) administrative and clinical data on Sicilian patients admitted to acute care hospitals and (2) data from the influenza virological surveillance of 10 European countries (FluNet database). All Sicilian patients diagnosed with at least 1 ICD-9 CM code for influenza (487.0, 487.1 and 487.9) were considered influenza cases.
  
  
  RESULTS
  Overall, 2,880 patients with an ICD-9 CM code attributable to influenza were hospitalized in Sicily: 2,119 (73.6%) were admitted from November to April, whereas 761 (26.4%) were admitted from May to October. In the 3 years studied, the analyzed European influenza surveillance systems recorded a peak of laboratory-confirmed influenza activity from November to April with 36,753 (99.7%) influenza cases, whereas only 124 cases (0.3%) were observed from May to October.
  
  
  CONCLUSIONS
  In Sicily, more than one quarter of all hospital admissions with an ICD-9 CM code for influenza were observed in the months with a negligible circulation of influenza viruses. Our findings show that several hospital discharge records included ICD-9 CM codes for influenza with low levels of sensitivity, specificity and/or appropriateness for clinical information and support the need for improving medical education on the epidemiology and hospital management of influenza cases.
authors: Department of Sciences for Health Promotion and Mother-Child Care 'G. D'Alessandro', University of Palermo, Palermo, Italy.
authors: Emanuele
authors: E
authors: Amodio
authors: Fabio
authors: F
authors: Tramuto
authors: Claudio
authors: C
authors: Costantino
authors: Vincenzo
authors: V
authors: Restivo
authors: Carmelo
authors: C
authors: Maida
authors: Giuseppe
authors: G
authors: Calamusa
authors: Francesco
authors: F
authors: Vitale
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005060:Europe; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007251:Influenza, Human / Q000453:epidemiology*; D038801:International Classification of Diseases / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D010343:Patient Admission / Q000706:statistics & numerical data*; D010351:Patient Discharge / Q000706:statistics & numerical data*; D062486:Public Health Surveillance; D015203:Reproducibility of Results; D012621:Seasons; D055815:Young Adult