title: Variability of oxygenation in possible hepatopulmonary syndrome: effects of requiring two abnormal arterial blood gas results for diagnosis.
abstract: OBJECTIVE
  Hepatopulmonary syndrome (HPS) affects 10-32 % of patients with cirrhosis and is defined by liver abnormalities, intrapulmonary vascular dilatations (IPVDs), and abnormal oxygenation. However, published criteria for abnormal oxygenation are inconsistent. We sought to evaluate variation in oxygenation over time and to compare various diagnostic criteria for validity, based on their diagnostic stability over time and ability to identify patients with clinically relevant findings.
  
  
  METHODS
  We retrospectively analyzed oxygenation and diffusion capacity in patients with liver abnormalities and IPVDs who had ≥ 2 arterial blood gases (ABGs) at the University of Toronto or Universite de Montreal. We compared the performance of nine possible oxygenation criteria for HPS and for each explored whether validity improved when requiring two consecutive abnormal ABGs on different days.
  
  
  RESULTS
  Mean PaO2 was 68.4 mmHg and annual within-patient coefficient of variation 6.3 % (58 patients). Applying published criteria, 8.6-15.5 % of patients initially diagnosed with HPS no longer met the criterion for HPS on a subsequent ABG (re-classified). Requiring two consecutive abnormal ABGs on different days: (1) reduced the proportion of re-classified patients (9/9 criteria); (2) identified patients with more rapid progression in hypoxemia and greater difference in rate of progression between HPS and non-HPS (7/9 criteria); and (3) identified patients with lower diffusion and a larger difference in diffusion between HPS and non-HPS (8/9 criteria).
  
  
  CONCLUSIONS
  Oxygenation is variable in this population, and requiring two abnormal results might reduce misdiagnosis and better differentiate patients with and without HPS according to clinically relevant markers of disease.
authors.affiliation: Department of Medicine, University of Toronto, Suite 6042, Bond Wing, 30 Bond St., Toronto, ON, M5B 1W8, Canada, GuptaS@smh.ca.
authors.forename: Samir
authors.initials: S
authors.lastname: Gupta
authors.forename: Dhruv
authors.initials: D
authors.lastname: Nayyar
authors.forename: Gilles
authors.initials: G
authors.lastname: Pomier-Layrargues
mesh_terms: D001784:Blood Gas Analysis; D005260:Female; D020065:Hepatopulmonary Syndrome / Q000097:blood*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009864:Ontario; D010100:Oxygen / Q000097:blood*; D011792:Quebec; D012129:Respiratory Function Tests; D012189:Retrospective Studies
chemical_list: D010100:Oxygen