title: FRAX® tool, the WHO algorithm to predict osteoporotic fractures: the first analysis of its discriminative and predictive ability in the Spanish FRIDEX cohort.
abstract: BACKGROUND
  The WHO has recently published the FRAX® tool to determine the absolute risk of osteoporotic fracture at 10 years. This tool has not yet been validated in Spain.
  
  
  METHODS
  A prospective observational study was undertaken in women in the FRIDEX cohort (Barcelona) not receiving bone active drugs at baseline. Baseline measurements: known risk factors including those of FRAX® and a DXA. Follow up data on self-reported incident major fractures (hip, spine, humerus and wrist) and verified against patient records. The calculation of absolute risk of major fracture and hip fracture was by FRAX® website. This work follows the guidelines of the STROBE initiative for cohort studies. The discriminative capacity of FRAX® was analyzed by the Area Under Curve (AUC), Receiver Operating Characteristics (ROC) and the Hosmer-Lemeshow goodness-of-fit test. The predictive capacity was determined using the ratio of observed fractures/expected fractures by FRAX® (ObsFx/ExpFx).
  
  
  RESULTS
  The study subjects were 770 women from 40 to 90 years of age in the FRIDEX cohort. The mean age was 56.8 ± 8 years. The fractures were determined by structured telephone questionnaire and subsequent testing in medical records at 10 years. Sixty-five (8.4%) women presented major fractures (17 hip fractures). Women with fractures were older, had more previous fractures, more cases of rheumatoid arthritis and also more osteoporosis on the baseline DXA. The AUC ROC of FRAX® for major fracture without bone mineral density (BMD) was 0.693 (CI 95%; 0.622-0.763), with T-score of femoral neck (FN) 0.716 (CI 95%; 0.646-0.786), being 0.888 (CI 95%; 0.824-0.952) and 0.849 (CI 95%; 0.737-0.962), respectively for hip fracture. In the model with BMD alone was 0.661 (CI 95%; 0.583-0.739) and 0.779 (CI 95%; 0.631-0.929). In the model with age alone was 0.668 (CI 95%; 0.603-0.733) and 0.882 (CI 95%; 0.832-0.936). In both cases there are not significant differences against FRAX® model. The overall predictive value for major fracture by ObsFx/ExpFx ratio was 2.4 and 2.8 for hip fracture without BMD. With BMD was 2.2 and 2.3 respectively. Sensitivity of the four was always less than 50%. The Hosmer-Lemeshow test showed a good correlation only after calibration with ObsFx/ExpFx ratio.
  
  
  CONCLUSIONS
  The current version of FRAX® for Spanish women without BMD analysed by the AUC ROC demonstrate a poor discriminative capacity to predict major fractures but a good discriminative capacity for hip fractures. Its predictive capacity does not adjust well because leading to underdiagnosis for both predictions major and hip fractures. Simple models based only on age or BMD alone similarly predicted that more complex FRAX® models.
authors.affiliation: Department of Medicine, Universitat Autònoma de Barcelona-UAB, Psg Vall d'Hebrón 119-129, 08035 Barcelona, Spain. rafael.azagra@uab.cat
authors.forename: Rafael
authors.initials: R
authors.lastname: Azagra
authors.forename: Genís
authors.initials: G
authors.lastname: Roca
authors.forename: Gloria
authors.initials: G
authors.lastname: Encabo
authors.forename: Amada
authors.initials: A
authors.lastname: Aguyé
authors.forename: Marta
authors.initials: M
authors.lastname: Zwart
authors.forename: Sílvia
authors.initials: S
authors.lastname: Güell
authors.forename: Núria
authors.initials: N
authors.lastname: Puchol
authors.forename: Emili
authors.initials: E
authors.lastname: Gene
authors.forename: Enrique
authors.initials: E
authors.lastname: Casado
authors.forename: Pilar
authors.initials: P
authors.lastname: Sancho
authors.forename: Silvia
authors.initials: S
authors.lastname: Solà
authors.forename: Pere
authors.initials: P
authors.lastname: Torán
authors.forename: Milagros
authors.initials: M
authors.lastname: Iglesias
authors.forename: Maria Carmen
authors.initials: MC
authors.lastname: Gisbert
authors.forename: Francesc
authors.initials: F
authors.lastname: López-Expósito
authors.forename: Jesús
authors.initials: J
authors.lastname: Pujol-Salud
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Fernandez-Hermida
authors.forename: Ana
authors.initials: A
authors.lastname: Puente
authors.forename: Mireia
authors.initials: M
authors.lastname: Rosàs
authors.forename: Vicente
authors.initials: V
authors.lastname: Bou
authors.forename: Juan José
authors.initials: JJ
authors.lastname: Antón
authors.forename: Gustavo
authors.initials: G
authors.lastname: Lansdberg
authors.forename: Juan Carlos
authors.initials: JC
authors.lastname: Martín-Sánchez
authors.forename: Adolf
authors.initials: A
authors.lastname: Díez-Pérez
authors.forename: Daniel
authors.initials: D
authors.lastname: Prieto-Alhambra
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D015519:Bone Density / Q000502:physiology; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D058866:Osteoporotic Fractures / Q000175:diagnosis / Q000000981:diagnostic imaging* / Q000453:epidemiology*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012307:Risk Factors; D013030:Spain / Q000453:epidemiology; D014944:World Health Organization