[Differences in the predictive values of the FRAX™ tool between the Spanish and United Kingdom population and considerations about the intervention threshold]

[Prevalence of osteoporosis, estimation of probability of fracture and bone metabolism study in patients with newly diagnosed prostate cancer in the health area of Lugo]

OBJECTIVE

To study the prevalence of osteoporosis and fracture probability in patients diagnosed with prostate cancer.

DESIGN

Observational descriptive transversal study. SITE: Study performed from Primary Care of Lugo in collaboration with Rheumatology and Urology Services of our referral hospital.

PARTICIPANTS

Patients diagnosed with prostate cancer without bone metastatic disease from January to December 2012.

MAIN MEASUREMENTS

Epidemiologic, clinical, laboratory and densitometric variables involved in osteoporosis were collected. The likelihood of fracture was estimated by FRAX^® Tool.

RESULTS

Eighty-three patients met the inclusion criteria. None was excluded. The average age was 67 years. The Body Mass Index was 28.28. Twenty-five patients (30.1%) had previous osteoporotic fractures. Other prevalent risk factors were alcohol (26.5%) and smoking (22.9%). Eighty-two subjects had vitamin D below normal level (98.80%). Femoral Neck densitometry showed that 8.9% had osteoporosis and 54% osteopenia. The average fracture risk in this population, estimated by FRAX^®, was 2.63% for hip fracture and 5.28% for major fracture. Cut level for FRAX^® major fracture value without DXA >5% and ≥7.5% proposed by Azagra et al. showed 24 patients (28.92%) and 8 patients (9.64%) respectively.

CONCLUSIONS

The prevalence of osteoporosis in this population was very high. The more frequent risk factors associated with osteoporosis were: previous osteoporotic fracture, alcohol consumption, smoking and family history of previous fracture. The probability of fracture using femoral neck FRAX^® tool was low. Vitamin D deficiency was very common (98.8%).

A systematic review of intervention thresholds based on FRAX : A report prepared for the National Osteoporosis Guideline Group and the International Osteoporosis Foundation

This systematic review identified assessment guidelines for osteoporosis that incorporate FRAX. The rationale for intervention thresholds is given in a minority of papers. Intervention thresholds (fixed or age-dependent) need to be country-specific.

INTRODUCTION

In most assessment guidelines, treatment for osteoporosis is recommended in individuals with prior fragility fractures, especially fractures at spine and hip. However, for those without prior fractures, the intervention thresholds can be derived using different methods. The aim of this report was to undertake a systematic review of the available information on the use of FRAX® in assessment guidelines, in particular the setting of thresholds and their validation.

METHODS

We identified 120 guidelines or academic papers that incorporated FRAX of which 38 provided no clear statement on how the fracture probabilities derived are to be used in decision-making in clinical practice. The remainder recommended a fixed intervention threshold (n = 58), most commonly as a component of more complex guidance (e.g. bone mineral density (BMD) thresholds) or an age-dependent threshold (n = 22). Two guidelines have adopted both age-dependent and fixed thresholds.

RESULTS

Fixed probability thresholds have ranged from 4 to 20 % for a major fracture and 1.3-5 % for hip fracture. More than one half (39) of the 58 publications identified utilised a threshold probability of 20 % for a major osteoporotic fracture, many of which also mention a hip fracture probability of 3 % as an alternative intervention threshold. In nearly all instances, no rationale is provided other than that this was the threshold used by the National Osteoporosis Foundation of the USA. Where undertaken, fixed probability thresholds have been determined from tests of discrimination (Hong Kong), health economic assessment (USA, Switzerland), to match the prevalence of osteoporosis (China) or to align with pre-existing guidelines or reimbursement criteria (Japan, Poland). Age-dependent intervention thresholds, first developed by the National Osteoporosis Guideline Group (NOGG), are based on the rationale that if a woman with a prior fragility fracture is eligible for treatment, then, at any given age, a man or woman with the same fracture probability but in the absence of a previous fracture (i.e. at the 'fracture threshold') should also be eligible. Under current NOGG guidelines, based on age-dependent probability thresholds, inequalities in access to therapy arise especially at older ages (≥70 years) depending on the presence or absence of a prior fracture. An alternative threshold using a hybrid model reduces this disparity.

CONCLUSION

The use of FRAX (fixed or age-dependent thresholds) as the gateway to assessment identifies individuals at high risk more effectively than the use of BMD. However, the setting of intervention thresholds needs to be country-specific.

[FRAX® thresholds to identify people with high or low risk of osteoporotic fracture in Spanish female population]

BACKGROUND AND OBJECTIVE

To detect FRAX(®) threshold levels that identify groups of the population that are at high/low risk of osteoporotic fracture in the Spanish female population using a cost-effective assessment.

PATIENTS AND METHODS

This is a cohort study. Eight hundred and sixteen women 40-90 years old selected from the FRIDEX cohort with densitometry and risk factors for fracture at baseline who received no treatment for osteoporosis during the 10 year follow-up period and were stratified into 3 groups/levels of fracture risk (low<10%, 10-20% intermediate and high>20%) according to the real fracture incidence.

RESULTS

The thresholds of FRAX(®) baseline for major osteoporotic fracture were: low risk<5; intermediate ≥ 5 to <7.5 and high ≥ 7.5. The incidence of fracture with these values was: low risk (3.6%; 95% CI 2.2-5.9), intermediate risk (13.7%; 95% CI 7.1-24.2) and high risk (21.4%; 95% CI12.9-33.2). The most cost-effective option was to refer to dual energy X-ray absorptiometry (DXA-scan) for FRAX(®)≥ 5 (Intermediate and high risk) to reclassify by FRAX(®) with DXA-scan at high/low risk. These thresholds select 17.5% of women for DXA-scan and 10% for treatment. With these thresholds of FRAX(®), compared with the strategy of opportunistic case finding isolated risk factors, would improve the predictive parameters and reduce 82.5% the DXA-scan, 35.4% osteoporosis prescriptions and 28.7% cost to detect the same number of women who suffer fractures.

CONCLUSIONS

The use of FRAX ® thresholds identified as high/low risk of osteoporotic fracture in this calibration (FRIDEX model) improve predictive parameters in Spanish women and in a more cost-effective than the traditional model based on the T-score ≤ -2.5 of DXA scan.

Validation of the FRAX predictive model for major osteoporotic fracture in a historical cohort of Spanish women

FRAX is a fracture risk assessment tool to estimate the 10-yr probability of a major osteoporotic fracture or a hip fracture. The aim of the study was to assess the predictive ability of FRAX for major osteoporotic fracture in a cohort of Spanish women. The study was based on a retrospective cohort of women aged 40-90 yr. Patients were followed from their first bone densitometry to the first major osteoporotic fracture event (forearm, proximal humerus, clinical spine, or hip fracture) or for 10 yr whichever comes first. A total of 1231 women were included. Bone mineral density data and self-reported data on risk factors for fracture were obtained. The predictive ability of FRAX was assessed by analyzing calibration and discrimination, with the calculation of observed-to-expected (O/E) fracture ratios and the receiver operating characteristic (ROC) curve, respectively. A total of 222 women (18.1%) reported at least 1 fracture after the first assessment. The incidence of fracture was 14 (95% confidence interval [CI]: 10-17), 19 (95% CI: 15-23), 28 (95% CI: 21-36), and 67 (95% CI: 8-125) cases per 1000 woman-years in women aged <55, 55-64, 65-74, and ≥75 yr, respectively. The O/E ratio was 3.9 (95% CI: 3.4-4.5; p<0.0001). The area under the ROC curve was 61% (95% CI: 57-65%). FRAX underestimated the risk of major osteoporotic fracture in this cohort of Spanish women, particularly in those with a low risk of fracture according to the clinical factors used in the FRAX tool. Our findings highlight the need for validation studies of FRAX in Spain.

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

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 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.