Objectives: To enhance the public awareness and facilitate diagnosis of osteoporosis, we aim to develop a new Chinese Osteoporosis Screening Algorithm (COSA) to identify people at high risk of osteoporosis. Methods: A total of 4747 postmenopausal women and men aged ! 50 from the Hong Kong Osteoporosis Study were randomly split into a development (N ¼ 2373) and an internal validation cohort (N ¼ 2374). An external validation cohort comprising 1876 community-dwelling subjects was used to evaluate the positive predictive value (PPV). Results: Among 11 predictors included, age, sex, weight, and history of fracture were significantly associated with osteoporosis after correction for multiple testing. Age- and sex-stratified models were developed due to the presence of significant sex and age interactions. The area under the curve of the COSA in the internal validation cohort was 0.761 (95% CI, 0.711e0.811), 0.822 (95% CI, 0.792e0.851), and 0.946 (95% CI, 0.908e0.984) for women aged < 65, women aged ! 65, and men, respectively. The COSA demonstrated improved reclassification performance when compared to Osteoporosis Self-Assessment Tool for Asians. In the external validation cohort, the PPV of COSA was 40.6%, 59.4%, and 19.4% forwomen aged < 65, women aged ! 65, and men, respectively. In addition, COSA > 0 was associated with an increased 10-year risk of hip fracture in women ! 65 (OR, 4.65; 95% CI, 2.24e9.65) and men (OR, 11.51; 95% CI, 4.16e31.81). Conclusions We have developed and validated a new osteoporosis screening algorithm, COSA, specific for Hong Kong Chinese.

Objectives: To evaluate the association of illicit drug use with bone mineral density (BMD) and hip geometric parameters at the narrow neck. Methods: This is a cross-sectional matched cohort study conducted in the Hong Kong Chinese population. Associations with illicit drug use were estimated using linear regression for BMD (lumbar spine and femoral neck) and hip geometrical parameters (cross-sectional area [CSA], cross-sectional moment of inertia [CSMI], section modulus [SM], average cortical thickness [ACT] and BMD at the narrow neck) after adjusting for age, body mass index (BMI), smoking status, drinking status, physical activity, and history of antipsychotic and antidepressant use. Mean difference and 95% confidence intervals (95% CI) were calculated between 108 illicit drug users and 108 controls using an adjusted linear model and cluster-robust standard errors after matching by age and sex. The false discovery rate was used to correct for multiple testing. Results: Illicit drug users had a significantly lower BMD (g/cm2 ) at the lumbar spine (mean difference: -0.062; 95% CI: -0.108 to − 0.015), and femoral neck (mean difference: -0.058; 95% CI: -0.106 to − 0.010) in the fully adjusted model. Illicit drug users also had a significantly lower CSA (mean difference: -0.238 cm2 ; 95% CI: -0.462 to − 0.013), ACT (mean difference: -0.018 cm; 95% CI: -0.030 to − 0.006) and BMD (mean difference: -0.070 g/ cm2 ; 95% CI: -0.128 to − 0.012) at the narrow neck. Conclusions Illicit drug use is associated with lower BMD and bone strength. Future studies evaluating the risk of illicit drug use with fragility fracture are warranted.