title: Explanatory value of the Ability Index as assessed by cardiologists and patients with congenital heart disease.
abstract: BACKGROUND
  The Ability Index was developed to classify patients with congenital heart disease into four functional classes. Functional class is typically determined by the cardiologist, based on data from a clinical interview. The validity of the Ability Index as assessed by the patient has never been scrutinized.
  
  
  OBJECTIVE
  We tested the agreement between cardiologists and patients in assessing functional status using the Ability Index and compared the accuracy of the two assessments in explaining patient-reported outcomes (PRO).
  
  
  METHODS
  The Ability Index Scale was completed for 57 patients, independently by cardiologists and patients. Cohen's Kappa coefficient with quadratic weighting (K(w)) was calculated. The area under the receiver operating characteristic (ROC) curve (AUC) (=C-index) was used to test the accuracy of the Ability Index in explaining PRO, as assessed by the cardiologist or the patient.
  
  
  RESULTS
  Agreement was observed in 61.4% of the patients. The K(w) was 0.55, showing a moderate agreement; and the R(2) was 0.29, displaying a limited shared variance. The AUC for cardiologists' assessments of the Ability Index in explaining PRO was consistently lower than the AUC for patients' assessments. The appraisal of the patients was more accurate.
  
  
  CONCLUSIONS
  When cardiologists and patients are assessing functional status using the Ability Index, two different constructs are measured. These assessments cannot be interchanged, but should be used complementarily. Because the assessment of the patients regarding the Ability Index is more precise in terms of explaining PRO, it could be valuable as a simple crude marker to identify patients at risk for poor functional and psychosocial outcomes.
authors.affiliation: The Heart Center, Rigshospitalet, Copenhagen University Hospital, Denmark. dorthe@overgaard.mail.dk
authors.forename: Dorthe
authors.initials: D
authors.lastname: Overgaard
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Schrader
authors.forename: Karen Holst
authors.initials: KH
authors.lastname: Lisby
authors.forename: Catriona
authors.initials: C
authors.lastname: King
authors.forename: Rie Friis
authors.initials: RF
authors.lastname: Christensen
authors.forename: Helena Friis
authors.initials: HF
authors.lastname: Jensen
authors.forename: Philip
authors.initials: P
authors.lastname: Moons
mesh_terms: D000293:Adolescent; D000328:Adult; D001007:Anxiety / Q000175:diagnosis / Q000523:psychology; D019540:Area Under Curve; D003430:Cross-Sectional Studies; D003863:Depression / Q000175:diagnosis / Q000523:psychology; D005260:Female; D006304:Health Status; D006305:Health Status Indicators; D006330:Heart Defects, Congenital / Q000145:classification* / Q000175:diagnosis / Q000503:physiopathology / Q000523:psychology; D006801:Humans; D007407:Interviews as Topic; D008297:Male; D015588:Observer Variation; D010361:Patients / Q000523:psychology; D010549:Personal Satisfaction; D010820:Physicians / Q000523:psychology; D011237:Predictive Value of Tests; D011788:Quality of Life; D012372:ROC Curve; D015203:Reproducibility of Results; D057566:Self Report; D060685:Sense of Coherence; D011795:Surveys and Questionnaires; D055815:Young Adult