title: The impact of the present on admission indicator on the accuracy of administrative data for carotid endarterectomy and stenting.
abstract: BACKGROUND
  Administrative data are often hampered by coding errors, absent data, and the difficulty of distinguishing pre-existing conditions from perioperative complications. We evaluated whether the introduction of the present on admission (POA) indicator improved outcome analysis of carotid endarterectomy (CEA) and carotid angioplasty and stenting (CAS) using administrative data.
  
  
  METHODS
  State inpatient databases from California (2005-2008), New York (2008), and New Jersey (2008) were used to identify patients undergoing CAS and CEA. We first analyzed morbidity data without the POA indicator, using International Classification of Diseases, Ninth Revision complication codes (eg, 997.02, iatrogenic cerebrovascular infarction or hemorrhage, postoperative stroke) and diagnosis codes (eg, 433.11, occlusion and stenosis of the carotid artery with cerebral infarction). Then, we applied the POA indicator to both diagnosis and complication codes and calculated the proportion of events that were labeled POA. Symptom status and perioperative stroke rate were compared using these coding approaches.
  
  
  RESULTS
  We identified 21,639 patients who underwent CEA and 3688 patients who underwent CAS. Without the POA indicator, the complication code for stroke indicated a postoperative stroke rate of 1.4% for CEA and 2.4% for CAS. After applying the POA indicator, 54% (CEA) and 62% (CAS) of these strokes were labeled POA. These POA strokes were either preoperative or intraoperative events. Proportion of symptomatic patients ranged from 7% to 16% for CEA and from 5% to 22% for CAS. Perioperative stroke rate was the lowest in the POA method (1.1% CEA, 1.8% CAS) compared with two other methods without POA information (1.4% and 9.5% CEA and 2.4% and 16.4% CAS). Kappa indicated a poor (0.2) to fair (0.7) agreement between these approaches.
  
  
  CONCLUSIONS
  Administrative data has known limitations for assignment of symptom status and nonfatal perioperative outcomes. Given the uncertain timing of POA events as preoperative vs intraoperative and its apparent underestimation of the perioperative stroke rate, the use of administrative data even with the POA indicator for symptom status and non-fatal outcomes after CEA and CAS is hazardous.
authors.affiliation: Division of Vascular and Endovascular Surgery, Department of Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Mass.
authors.forename: Margriet
authors.initials: M
authors.lastname: Fokkema
authors.affiliation: Department of Surgery, Division of Vascular Surgery, University Medical Center, Utrecht, The Netherlands.
authors.forename: Rob
authors.initials: R
authors.lastname: Hurks
authors.affiliation: Division of Vascular and Endovascular Surgery, Department of Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Mass.
authors.forename: Thomas
authors.initials: T
authors.lastname: Curran
authors.affiliation: Division of Vascular and Endovascular Surgery, Department of Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Mass.
authors.forename: Rodney P
authors.initials: RP
authors.lastname: Bensley
authors.affiliation: Division of Vascular and Endovascular Surgery, Department of Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Mass.
authors.forename: Allen D
authors.initials: AD
authors.lastname: Hamdan
authors.affiliation: Division of Vascular and Endovascular Surgery, Department of Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Mass.
authors.forename: Mark C
authors.initials: MC
authors.lastname: Wyers
authors.affiliation: Department of Surgery, Division of Vascular Surgery, University Medical Center, Utrecht, The Netherlands.
authors.forename: Frans L
authors.initials: FL
authors.lastname: Moll
authors.affiliation: Division of Vascular and Endovascular Surgery, Department of Surgery, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Mass. Electronic address: mscherme@bidymc.harvard.edu.
authors.forename: Marc L
authors.initials: ML
authors.lastname: Schermerhorn
mesh_terms: D017130:Angioplasty / Q000009:adverse effects / Q000295:instrumentation* / Q000401:mortality; D058070:Asymptomatic Diseases; D002340:Carotid Artery Diseases / Q000150:complications / Q000175:diagnosis / Q000401:mortality / Q000601:surgery / Q000628:therapy*; D015897:Comorbidity; D016208:Databases, Factual; D016894:Endarterectomy, Carotid / Q000009:adverse effects / Q000401:mortality; D006801:Humans; D038801:International Classification of Diseases; D010343:Patient Admission; D010351:Patient Discharge; D064266:Preexisting Condition Coverage; D015203:Reproducibility of Results; D015607:Stents; D020521:Stroke / Q000175:diagnosis* / Q000209:etiology / Q000401:mortality; D016896:Treatment Outcome; D014481:United States