title: Statistical combination schemes of repeated diagnostic test data.
abstract: OBJECTIVE
  When diagnostic tests are repeated and combined, a number of schemes may be adopted. Guidelines for their interpretations are required.
  
  
  METHODS
  Three combination schemes, "and" (A), "or" (O), and "majority" (M), are considered. To evaluate these schemes, dependency by specifying kappa values quantifying repeated test agreement was structured. In a pilot study, the combined accuracies of magnetic resonance imaging using six different pulse sequences of medial collateral ligaments of the elbows of 28 cadavers, with eight having lesions artificially created surgically, were examined. Images were evaluated simultaneously by using a five-point ordinal scale. For each pulse sequence, individuals for whom the diagnosis varied from once to three repetitions were considered.
  
  
  RESULTS
  Scheme M improves diagnostic accuracy when sensitivity and specificity of a single test exceed 0.5, with maximal improvement at 0.79. Under scheme A, sensitivity decreases to 0.38-0.59. Under scheme O, sensitivity increases to 0.53-0.79. Scheme M yields a small improvement, reaching 0.50-0.71. Under scheme A, specificity increases to 0.95-0.98. Under scheme O, specificity decreases to 0.91-0.98. Scheme M also yields a small improvement, reaching 0.94-0.98.
  
  
  CONCLUSIONS
  Scheme A is recommended for ruling in diagnoses, scheme O is recommended for ruling out diagnoses, and scheme M is neutral. Consequently, different schemes may be used to optimize the target diagnostic accuracy.
authors.affiliation: Department of Radiology (L-2), Brigham and Women's Hospital, Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA. zou@bwh.harvard.edu
authors.forename: Kelly H
authors.initials: KH
authors.lastname: Zou
authors.forename: Jui G
authors.initials: JG
authors.lastname: Bhagwat
authors.forename: John A
authors.initials: JA
authors.lastname: Carrino
mesh_terms: D000465:Algorithms; D003627:Data Interpretation, Statistical; D006801:Humans; D007089:Image Enhancement / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D016247:Information Storage and Retrieval / Q000379:methods; D008279:Magnetic Resonance Imaging / Q000379:methods*; D017888:Medial Collateral Ligament, Knee / Q000293:injuries* / Q000473:pathology*; D015588:Observer Variation; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013382:Subtraction Technique