title: Variations in the associations between psychiatric comorbidity and hospital mortality according to the method of identifying psychiatric diagnoses.
abstract: OBJECTIVE
  Little is known about associations between psychiatric comorbidity and hospital mortality for acute medical conditions. This study examined if associations varied according to the method of identifying psychiatric comorbidity and agreement between the different methods.
  
  
  METHODS
  The sample included 31,218 consecutive admissions to 168 Veterans Affairs facilities in 2004 with a principle diagnosis of congestive heart failure (CHF) or pneumonia. Psychiatric comorbidity was identified by: (1) secondary diagnosis codes from index admission, (2) prior outpatient diagnosis codes, (3) and prior mental health clinic visits. Generalized estimating equations (GEE) adjusted in-hospital mortality for demographics, comorbidity, and severity of illness, as measured by laboratory data.
  
  
  RESULTS
  Rates of psychiatric comorbidities were 9.0% using inpatient diagnosis codes, 27.4% using outpatient diagnosis codes, and 31.0% using mental health visits for CHF and 14.5%, 33.1%, and 34.1%, respectively, for pneumonia. Agreement was highest for outpatient codes and mental health visits (kappa = 0.51 for pneumonia and 0.50 for CHF). In GEE analyses, the adjusted odds of death for patients with psychiatric comorbidity were lower when such comorbidity was identified by mental health visits for both pneumonia (odds ratio [OR] = 0.85; P = .009) and CHF (OR = 0.70; P < .001) and by inpatient diagnosis for pneumonia (OR = 0.63; P < or = .001) but not for CHF (OR = 0.75; P = .128). The odds of death were similar (P > .2) for psychiatric comorbidity as identified by outpatient codes for pneumonia (OR = 1.04) and CHF (OR = 0.93).
  
  
  CONCLUSIONS
  The method used to identify psychiatric comorbidities in acute medical populations has a strong influence on the rates of identification and the associations between psychiatric illnesses with hospital mortality.
authors.affiliation: The Center for Research in the Implementation of Innovative Strategies in Practice (CRIISP), Iowa City VA Healthcare System, Iowa City, IA, USA. thad-abrams@uiowa.edu
authors.forename: Thad E
authors.initials: TE
authors.lastname: Abrams
authors.forename: Mary
authors.initials: M
authors.lastname: Vaughan-Sarrazin
authors.forename: Gary E
authors.initials: GE
authors.lastname: Rosenthal
mesh_terms: D017677:Age Distribution; D000368:Aged; D000369:Aged, 80 and over; D002423:Cause of Death; D015331:Cohort Studies; D015897:Comorbidity; D005260:Female; D005500:Follow-Up Studies; D006333:Heart Failure / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D017052:Hospital Mortality / Q000639:trends*; D006760:Hospitalization / Q000706:statistics & numerical data; D006787:Hospitals, Veterans; D006801:Humans; D015994:Incidence; D038801:International Classification of Diseases; D016015:Logistic Models; D008297:Male; D001523:Mental Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D008875:Middle Aged; D016017:Odds Ratio; D011014:Pneumonia / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D011336:Probability; D018570:Risk Assessment; D012720:Severity of Illness Index; D017678:Sex Distribution