title: Evaluating the quality of longitudinal statistical applications in original publications on Alzheimer's disease.
abstract: OBJECTIVE
  To evaluate the quality of longitudinal statistical applications in published studies on Alzheimer's disease (AD).
  
  
  METHODS
  A 21-item instrument, the Quality of Longitudinal AD Studies (QLADS), was developed by the research team (4 biostatisticians, 1 neuroepidemiologist, and 1 neurologist). All items were extensively discussed within the team for content validity. After pilot testing on 5 publications, the instrument was revised and tested for reliability with a sample of 40 published longitudinal AD studies randomly sampled from MEDLINE.
  
  
  RESULTS
  Item-specific test-retest reliability coefficients for QLADS ranged from 0.53 to 1.00 with the associated standard error (SE) ranging from 0.02 to 0.13. The test-retest reliability for the overall score over the 21 items was high (intraclass correlation coefficient (ICC) = 0.94, 95% CI 0.90, 0.97). Item-specific inter-rater reliability coefficients for QLADS ranged from 0.46 to 1.00 with the associated SE ranging from 0.07 to 0.18. The inter-rater reliability for the overall score was also high (ICC = 0.87, 95% CI 0.77, 0.93).
  
  
  CONCLUSIONS
  This study indicates that the quality of longitudinal statistical applications in AD publications can be reliably assessed.
authors.affiliation: Division of Biostatistics, Washington University, St. Louis, MO 63110, USA. chengjie@wubios.wustl.edu
authors.forename: Chengjie
authors.initials: C
authors.lastname: Xiong
authors.forename: Yuxiao
authors.initials: Y
authors.lastname: Tang
authors.forename: Gerald
authors.initials: G
authors.lastname: van Belle
authors.forename: J Philip
authors.initials: JP
authors.lastname: Miller
authors.forename: Lenore J
authors.initials: LJ
authors.lastname: Launer
authors.forename: John C
authors.initials: JC
authors.lastname: Morris
mesh_terms: D000368:Aged; D000544:Alzheimer Disease; D003627:Data Interpretation, Statistical; D005500:Follow-Up Studies; D006801:Humans; D008137:Longitudinal Studies; D015588:Observer Variation; D011642:Publications / Q000592:standards* / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D012107:Research Design / Q000592:standards* / Q000706:statistics & numerical data*