title: The role of readily available clinical, laboratory and radiologic findings in distinguishing a/H1N1/2009 influenza from other causes of acute febrile respiratory illness under pandemic conditions.
abstract: BACKGROUND
  During an influenza pandemic, clinicians need easily available clinical and laboratory criteria to distinguish influenza from similar respiratory illnesses. We compared A/H1N1/2009-polymerase chain reaction (PCR)-positive and matched PCR-negative hospitalized patients with suspected H1N1 influenza to identify factors that could assist physicians at patient admission.
  
  
  OBJECTIVE
  To identify factors significantly associated with A/ H1N1/2009 infection.
  
  
  METHODS
  A group of 145 patients with PCR-confirmed A/H1N1 2009 influenza admitted between 27 May 2009 and 3 December 2009 was matched with 145 PCR-negative patients by age, epidemiological week and pregnancy status. Epidemiological and clinical parameters and radiological findings on initial chest X-ray were compared between the two groups.
  
  
  RESULTS
  Asthma (PCR+ 26%, PCR- 12%, P = 0.006) and military service (PCR+ 13%, PCR- 4%, P = 0.15) were associated with PCR-positive status in non-pregnant patients. At presentation, fever, cough, myalgia and fulfilling the pandemic influenza case definition were significantly more frequent in nonpregnant PCR+ patients (62/90/43/59% in PCR+ versus 38/69/30/35% in PCR-). In pregnant patients, fever and fulfilling the case definition were significantly associated with PCR-positive status. Mean leukocyte and absolute lymphocyte counts were significantly lower in both pregnant and nonpregnant PCR-positive patients. Significantly more PCR-negative non-pregnant patients (43% vs. 22% PCR+, P = 0.004) had abnormal chest X-ray (CXR) findings on presentation. In PCR-positive patients, patchy consolidation and interstitial infiltrates were the most common abnormalities.
  
  
  CONCLUSIONS
  Under the conditions generated by the A/ H1 1/2009 pandemic, radiological findings did not distinguish reliably between influenza and other febrile respiratory illnesses. Asthma, military service, the pandemic case definition (particularly fever, cough and myalgia)
authors.affiliation: Infectious Diseases Unit, Assaf Harofeh Medical Center, Zerifin, Israel. reba_vaca@hotmail.com
authors.forename: Rebekah
authors.initials: R
authors.lastname: Karplus
authors.forename: Miriam
authors.initials: M
authors.lastname: Weinberger
authors.forename: Ronit
authors.initials: R
authors.lastname: Zaidenstein
authors.forename: Lili
authors.initials: L
authors.lastname: Goldshtein
authors.forename: Noam
authors.initials: N
authors.lastname: Natif
authors.forename: Gabriela
authors.initials: G
authors.lastname: Gayer
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D004279:DNA, Viral / Q000032:analysis*; D003937:Diagnosis, Differential; D005260:Female; D005334:Fever / Q000175:diagnosis* / Q000453:epidemiology / Q000209:etiology; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000235:genetics* / Q000302:isolation & purification; D007251:Influenza, Human / Q000150:complications / Q000175:diagnosis* / Q000453:epidemiology; D007557:Israel / Q000453:epidemiology; D008297:Male; D058873:Pandemics; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology; D012140:Respiratory Tract Diseases / Q000175:diagnosis / Q000453:epidemiology / Q000209:etiology*; D012189:Retrospective Studies; D055815:Young Adult
chemical_list: D004279:DNA, Viral