Possible FRAX-based intervention thresholds for a cohort of Chinese postmenopausal women
E Cheung1, C-L Cheung, A W C Kung
1Department of Medicine, United Christian Hospital, Hong Kong, China, c4366@hotmail.com.
Summary:
A total of 2,266 postmenopausal Chinese women were followed for 4.5 years to determine the incidence of new fractures. The positive predictive value, negative predictive value, sensitivity and specificity of different treatment strategies were compared. Using a fixed optimal threshold calculated from receiver operating characteristics (ROC) curve had the highest sensitivity but lowest specificity.
Introduction:
There is no specific intervention threshold based on FRAX to guide treatment for Asian populations. This prospective study sought to determine the impact of applying different intervention thresholds to a cohort of Chinese postmenopausal women.
Methods:
This study was part of the Hong Kong Osteoporosis Study. A total of 2,266 treatment-naïve postmenopausal women underwent clinical risk factor and BMD assessments. The subjects were followed to assess fractures. We calculated the FRAX probability of major osteoporotic fractures corresponding to women with prior fractures but no other clinical risk factors. Different treatment strategies which include treating women with prior fractures, women with age-specific FRAX probability corresponding to those with prior fractures, women with osteoporosis as well as women with FRAX probability above a fixed cut-off based on optimizing sensitivity and specificity on the ROC curve were compared.
Results:
The mean age at baseline was 62.1 ± 8.5 years, and the mean follow-up time was 4.5 ± 2.8 years. One hundred six new major osteoporotic fractures were reported. An optimal (FRAX, with BMD) cut-off point of 9.95 % was identified. All strategies had negative predictive value of >90 %. Using a fixed cut-off had the highest sensitivity (62.3 %) but lowest specificity (73.5 %) and positive predictive value (10.3 %). Using a fixed cut-off would direct treatment from younger women with lower absolute risk to elderly women with higher absolute risk.
Conclusion:
Targeting only women with prior fractures is unlikely to reduce fracture burden. Other treatment strategies with higher sensitivity need to be considered but they have different shortcomings.