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Open Access Research article

FRAX® tool, the WHO algorithm to predict osteoporotic fractures: the first analysis of its discriminative and predictive ability in the Spanish FRIDEX cohort

Rafael Azagra123*, Genís Roca34, Gloria Encabo5, Amada Aguyé6, Marta Zwart37, Sílvia Güell8, Núria Puchol2, Emili Gene229, Enrique Casado10, Pilar Sancho11, Silvia Solà12, Pere Torán13, Milagros Iglesias2, Maria Carmen Gisbert14, Francesc López-Expósito115, Jesús Pujol-Salud16, Yolanda Fernandez-Hermida173, Ana Puente18, Mireia Rosàs6, Vicente Bou19, Juan José Antón20, Gustavo Lansdberg21, Juan Carlos Martín-Sánchez22, Adolf Díez-Pérez23 and Daniel Prieto-Alhambra1723

Author Affiliations

1 Department of Medicine, Universitat Autònoma de Barcelona (UAB), Psg Vall d’Hebrón 119-129, 08035, Barcelona, Spain

2 Badia del Vallès Health Centre, Catalan Health Institute. USR-MN-IDIAP Jordi Gol. c/ Bética s/n, 08214, Barcelona, Badia del Vallès, Spain

3 Doctorate Program, Department of Medicine, Universitat Autònoma de Barcelona (UAB). Psg Vall d’Hebrón 119–129, 08035, Barcelona, Spain

4 Sant Llàtzer Health Centre, Sanitary Consortium of Terrassa. c/ de la Riba 62, 08221, Barcelona, Terrassa, Spain

5 Nuclear Medicine Service, Vall d’Hebrón University Hospital. Psg Vall d’Hebrón 119–129, 08035, Barcelona, Spain

6 Granollers Centre Health Centre, Catalan Health Institute. c/ Museu 19, 08400, Barcelona, Granollers, Spain

7 Can Gibert del Plà-Girona-2 Health Centre, Catalan Health Institute. c/ Sant Sebastià 50, 17005, Girona, Spain

8 Montcada i Reixach Health Centre, Catalan Health Institute. Psg de Jaume I s/n, 08110, Barcelona, Montcada i Reixac, Spain

9 Emergency Department, Hospital de Sabadell, Sanitary Consortium of Parc Taulí, Universitat Autònoma de Barcelona. Parc Tauli s/n, 08208, Barcelona, Sabadell, Spain

10 Rheumatology Department, Hospital de Sabadell, Sanitary Consortium of Parc Taulí, Universitat Autònoma de Barcelona. Parc Tauli s/n, 08208, Barcelona, Sabadell, Spain

11 Corbera de Llobregat Health Centre, Catalan Health Institute. c/ Buenos Aires, 9, 08757, Barcelona, Corbera de Llobregat, Spain

12 Emergency Department, University Hospital of Bellvitge, Catalan Health Institute. University of Barcelona. c/ de la Feixa Llarga s/n, 08907, Barcelona, L'Hospitalet de Llobregat, Spain

13 Primary Health Research Support Unit Metropolitana Nord, Catalan Health Institute-IDIAP Jordi Gol. Rambla 227, 08223, Barcelona, Sabadell, Spain

14 Cabrils Health Centre, Catalan Health Institute. c/ Cal Batalló 3, 08348, Cabrils, Barcelona, Spain

15 Bon Pastor Health Centre. Health Institute. c/ Mollerussa s/n, 08030, Barcelona, Spain

16 Balaguer Health Centre, Catalan Health Institute. Universitat de Lleida. c/ Àngel Guimerà, 24 25600, Lleida, Balaguer, Spain

17 Botnar Research Centre, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Oxford, OX3 7LD, UK

18 Taradell Health Centre, Catalan Health Institute, C. Passeig del Pujaló, 5, 08552, Barcelona, Taradell, Spain

19 Sanllehy Health Centre. Catalan Health Institute. Av. Mare de Déu de Montserrat, 16–18, 08024, Barcelona, Spain

20 Poble Sec 3B Health Centre, CAP Manso. Catalan Health Institute. c/ Manso, 19–27, 08015, Barcelona, Spain

21 Universidade de José do Rosàrio Vellano. UNIFENAS, Belo Horizonte. Rua Libano - Bairro Itapoã 66, Belo Horizonte, 31710-030, Minas Gerais, Brasil

22 Universitat Internacional de Catalunya (UIC), c/ Josep Trueta s/n 08195 Sant Cugat del Vallès, Barcelona, Spain

23 Institut Municipal d'Investigacions Mèdiques (IMIM)-Parc de Salut Mar, URFOA, Internal Medicine, Universitat Autònoma de Barcelona. Psg Marítim 25, 08003, Barcelona, Spain

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BMC Musculoskeletal Disorders 2012, 13:204  doi:10.1186/1471-2474-13-204

Published: 22 October 2012

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/design

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 analzsed 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.