title: Association of diagnostic coding with trends in hospitalizations and mortality of patients with pneumonia, 2003-2009.
abstract: BACKGROUND
  Recent reports suggest that the mortality rate of patients hospitalized with pneumonia has steadily declined. While this may be the result of advances in clinical care or improvements in quality, it may also represent an artifact of changes in diagnostic coding.
  
  
  OBJECTIVE
  To compare estimates of trends in hospitalizations and inpatient mortality among patients with pneumonia using 2 approaches to case definition: one limited to patients with a principal diagnosis of pneumonia, and another that includes patients with a secondary diagnosis of pneumonia if the principal diagnosis is sepsis or respiratory failure.
  
  
  METHODS
  Trends study using data from the 2003-2009 releases of the Nationwide Inpatient Sample.
  
  
  METHODS
  Change in the annual hospitalization rate and change in inpatient mortality over time.
  
  
  RESULTS
  From 2003 to 2009, the annual hospitalization rate for patients with a principal diagnosis of pneumonia declined 27.4%, from 5.5 to 4.0 per 1000, while the age- and sex-adjusted mortality decreased from 5.8% to 4.2% (absolute risk reduction [ARR], 1.6%; 95% CI, 1.4%-1.9%; relative risk reduction [RRR], 28.2%; 95% CI, 25.2%-31.2%). Over the same period, hospitalization rates of patients with a principal diagnosis of sepsis and a secondary diagnosis of pneumonia increased 177.6% from 0.4 to 1.1 per 1000, while inpatient mortality decreased from 25.1% to 22.2% (ARR, 3.0%; 95% CI, 1.6%-4.4%; RRR, 12%; 95% CI, 7.5%-16.1%); hospitalization rates for patients with a principal diagnosis of respiratory failure and a secondary diagnosis of pneumonia increased 9.3% from 0.44 to 0.48 per 1000 and mortality declined from 25.1% to 19.2% (ARR, 6.0%; 95% CI, 4.6%-7.3%; RRR, 23.7%; 95% CI, 19.7%-27.8%). However, when the 3 groups were combined, the hospitalization rate declined only 12.5%, from 6.3 to 5.6 per 1000, while the age- and sex-adjusted inpatient mortality rate increased from 8.3% to 8.8% (AR increase, 0.5%; 95% CI, 0.1%-0.9%; RR increase, 6.0%; 95% CI, 3.3%-8.8%). Over this same time frame, the age-, sex-, and comorbidity-adjusted mortality rate declined from 8.3% to 7.8% (ARR, 0.5%; 95% CI, 0.2%-0.9%; RRR, 6.3%; 95% CI, 3.8%-8.8%).
  
  
  CONCLUSIONS
  From 2003 to 2009, hospitalization and inpatient mortality rates for patients with a principal diagnosis of pneumonia decreased substantially, whereas hospitalizations with a principal diagnosis of sepsis or respiratory failure accompanied by a secondary diagnosis of pneumonia increased and mortality declined. However, when the 3 pneumonia diagnoses were combined, the decline in the hospitalization rate was attenuated and inpatient mortality was little changed, suggesting an association of these results with temporal trends in diagnostic coding.
authors.affiliation: Baystate Medical Center, 280 Chestnut St, Springfield, MA 01199, USA. peter.lindenauer@bhs.org
authors.forename: Peter K
authors.initials: PK
authors.lastname: Lindenauer
authors.forename: Tara
authors.initials: T
authors.lastname: Lagu
authors.forename: Meng-Shiou
authors.initials: MS
authors.lastname: Shieh
authors.forename: Penelope S
authors.initials: PS
authors.lastname: Pekow
authors.forename: Michael B
authors.initials: MB
authors.lastname: Rothberg
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D059019:Clinical Coding / Q000706:statistics & numerical data* / Q000639:trends; D016208:Databases, Factual; D003953:Diagnosis-Related Groups / Q000706:statistics & numerical data; D005260:Female; D017052:Hospital Mortality / Q000639:trends; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011014:Pneumonia / Q000175:diagnosis* / Q000401:mortality*; D012131:Respiratory Insufficiency / Q000175:diagnosis* / Q000453:epidemiology; D012189:Retrospective Studies; D018805:Sepsis / Q000175:diagnosis* / Q000453:epidemiology; D014481:United States / Q000453:epidemiology; D055815:Young Adult