title: National US estimates of recombinant tissue plasminogen activator use: ICD-9 codes substantially underestimate.
abstract: OBJECTIVE
  Current US estimates of recombinant tissue plasminogen activator (rt-PA) use have been based either on extrapolation of regional studies or on administrative database estimates, both of which may have inherent biases. We sought to compare the utilization of rt-PA in acute ischemic stroke in the MEDPAR database to another national hospital database with drug utilization information.
  
  
  METHODS
  Cases were defined as DRG 14,15, and 524 and ICD-9 code 99.1, which indicates cerebral thrombolysis, for fiscal year 2001 to 2004. Additionally, the Premier database was queried for rt-PA utilization documented in pharmacy records in those patients admitted for stroke. Change over time and difference between databases were tested using Poisson regression.
  
  
  RESULTS
  When comparing databases, rt-PA use, as identified by ICD-9 code 99.1, was only documented in 0.95% of stroke cases in 2004 in MEDPAR, and 1.2% in the Premier database, which slightly increased by 0.04% to 0.09% over time. Analysis of pharmacy billing records increased the estimate to 1.82%. Exclusion of cases younger than 65 years excluded 43% of cases treated with rt-PA. In 2004, 12.7% of cases receiving thrombolytic had either a TIA or a hemorrhagic stroke ICD-9 code.
  
  
  CONCLUSIONS
  We estimate the rate of rt-PA use in the United States to be 1.8% to 2.1% of ischemic stroke patients. The rate of thrombolytic use for ischemic stroke was slightly increasing between 2001 and 2004 at a rate of 0.04% to 0.09% per year. A significant proportion of patients treated with rt-PA are likely miscoded as either TIA or hemorrhagic stroke. We conservatively estimate that 10,800 to 12,600 patients received rt-PA in 2004.
authors.affiliation: University of Cincinnati College of Medicine, Department of Neurology, 231 Albert Sabin Way ML 0525, Cincinnati, Ohio 45267-0525, USA. dawn.kleindorfer@uc.edu
authors.forename: Dawn
authors.initials: D
authors.lastname: Kleindorfer
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Lindsell
authors.forename: Lawrence
authors.initials: L
authors.lastname: Brass
authors.forename: Walter
authors.initials: W
authors.lastname: Koroshetz
authors.forename: Joseph P
authors.initials: JP
authors.lastname: Broderick
mesh_terms: D002545:Brain Ischemia / Q000150:complications*; D016208:Databases, Factual; D011307:Drug Prescriptions / Q000706:statistics & numerical data; D004363:Drug Utilization / Q000706:statistics & numerical data / Q000639:trends; D005343:Fibrinolytic Agents / Q000627:therapeutic use*; D006801:Humans; D038801:International Classification of Diseases / Q000592:standards; D011994:Recombinant Proteins / Q000627:therapeutic use; D020521:Stroke / Q000188:drug therapy* / Q000209:etiology; D010959:Tissue Plasminogen Activator / Q000627:therapeutic use*; D014481:United States
chemical_list: D005343:Fibrinolytic Agents; D011994:Recombinant Proteins; D010959:Tissue Plasminogen Activator