[Precautions required on using the predictive thresholds of the FRAX® tool to decide the need for an axial bone density scan in the Spanish population]

A comparative study between the implementation of the FRIDEX calibration and the NOGG guideline in the management of osteoporosis in routine clinical practice

OBJECTIVE

The recent FRIDEX calibration proposed cost-effectiveness thresholds for the Spanish population. The aim of our study is to evaluate the impact of its application in routine clinical practice and to compare its thresholds with those of the National Osteoporosis Guideline Group (NOGG).

MATERIAL AND METHODS

Cross-sectional study in women referred to a bone densitometry unit who were not receiving antiresorptive therapy. The absolute risk of major fracture or hip fracture was calculated with the Spanish and British formulas of the FRAX^® tool using the intervention thresholds of the FRIDEX calibration and the NOGG guideline, respectively.

RESULTS

The study included 607 women with a median age of 59.4 (IQR=14) years. Treatment was initiated in 31.4% after bone mineral densitometry. With the application of the FRIDEX calibration, bone mineral density testing would have been indicated in 35.4% of the sample and treatment in 26.7%, reducing costs by 18.8% over a 5-year period. The NOGG guideline would have recommended testing in 32% and treatment in 21.3% of the participants, resulting in a reduction in costs of 35% over 5years, when compared with the standard approach. Agreement between the FRIDEX calibration and the NOGG guideline, as defined by Cohen's kappa coefficient, was low in terms of both diagnostic (0.16 [95%CI, 0.09-0.24]) and therapeutic indications (0.39 [95%CI, 0.31-0.47]).

CONCLUSIONS

The application of the FRIDEX calibration and the NOGG guideline improves efficiency in the management of osteoporosis, although the level of agreement between the two is low.

Impact of the NOGG and NOF Guidelines on the Indication of Bone Mineral Density in Routine Clinical Practice

The universal screening for osteoporosis by bone mineral density (BMD) is not feasible because of its unfavorable cost-benefit due to its low sensitivity. The aim of the present study was to estimate the population and economic impact of the diagnostic criteria of the National Osteoporosis Guideline Group (NOGG) and the National Osteoporosis Foundation (NOF) and assess the appropriateness of the BMD tests performed in routine clinical practice. A cross-sectional study was conducted in individuals referred for BMD testing who were not receiving antiresorptive therapy. The absolute risk of major and hip fracture was calculated using the British formula of the Fracture Risk Assessment Tool. NOGG and NOF guidelines diagnostic thresholds interventions were used. A total of 640 individuals were included, of which 95% were women, with a median age of 59.4 years (interquartile range = 14). When applying the NOGG criteria, BMD testing was recommended in 32.3% of the individuals, whereas this percentage increased to 75.6% with the NOF guidelines (p < 0.05). Regarding the appropriateness of the BMD tests performed, 31.9% were deemed appropriate according to both the NOGG and NOF guidelines, whereas 23.9% were considered inappropriate. In conclusion, the application of the NOGG and NOF guidelines led to a decrease in BMD indications, reducing costs and improving efficiency in the diagnostic management of osteoporosis, although variability exists between the guidelines.

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.