title: Benchmarks for designing two-stage studies using modified mini-mental state examinations: experience from the Women's Health Initiative Memory Study.
abstract: BACKGROUND
  The most efficient approach for studies examining the incidence of dementia involves a brief screening instrument to identify participants for more extensive testing to identify cognitive impairment. The modified mini-mental state examination (3MS) is commonly used as this initial screen in such two-stage designs, however its properties for this role require further study.
  
  
  OBJECTIVE
  We use data from the Women's Health Initiative Memory Study to contrast design options in two-stage designs.
  
  
  METHODS
  This trial enrolled 7251 participants with nine or more years of education who were aged 65-79 and followed an average of four to five years. Logistic regression was used to examine the case yields at varying two-stage 3MS cutpoints. The efficiency of using different examination schedules and restricting enrollment to higher risk women was examined.
  
  
  RESULTS
  Probable dementia is associated with marked decline in 3MS scores. The percentages of women classified with probable dementia ranged from 7.95% (3MS 85-88) to 50.0% (3MS < 70). The numbers [95% confidence interval] of enrolled women necessary to detect one case of probable dementia (four-year follow-up) for baseline 3MS scores of 100, 95, 90 and 85 were estimated as 1477 [389, 5618], 253 [134, 481], 53 [34, 85], and 14 [9, 23], respectively. Compared to annual testing, administration every two years increased the number of required enrollees by 11%, but decreased the number of test administrations by 46%.
  
  
  CONCLUSIONS
  Our findings are influenced by the characteristics of our study group, its rates of retention, and the study protocol, and may not fully generalize to other settings.
  
  
  CONCLUSIONS
  The 3MS can serve as an efficient basis for two-stage study designs and a cutpoint of < or = 88 is reasonable for populations with similar characteristics. Studies may improve efficiency by using the 3MS during screening to eliminate women with low risk for dementia and by conducting testing every two years.
authors.affiliation: Department of Public Health Sciences, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA. mespelan@wfubmc.edu
authors.forename: Mark A
authors.initials: MA
authors.lastname: Espeland
authors.forename: Stephen R
authors.initials: SR
authors.lastname: Rapp
authors.forename: Julia
authors.initials: J
authors.lastname: Robertson
authors.forename: Iris
authors.initials: I
authors.lastname: Granek
authors.forename: Carol
authors.initials: C
authors.lastname: Murphy
authors.forename: Marilyn
authors.initials: M
authors.lastname: Albert
authors.forename: Tamsen
authors.initials: T
authors.lastname: Bassford
mesh_terms: D000368:Aged; D035843:Biomedical Research / Q000379:methods*; D003704:Dementia / Q000175:diagnosis*; D005260:Female; D006801:Humans; D011581:Psychological Tests / Q000592:standards*; D012107:Research Design; D011795:Surveys and Questionnaires