Correlation of osteoporosis screening by quantitative ultrasound of calcaneus and Osteoporosis Self-Assessment Tool for Asians in Taiwanese.

BACKGROUND AND PURPOSE

The Osteoporosis Self-Assessment Tool for Asians (OSTA) index, originally developed for use in postmenopausal Asian populations, is an inexpensive, simple tool based on age and body weight. Calcaneal quantitative ultrasound (QUS) is another simple and low-cost instrument used to prescreen osteoporotic subjects. This study investigated the correlation between these 2 screening methods.

METHODS

OSTA indices were calculated in a total of 3,456 women aged 40 to 95 years (mean, 59.5 +/- 11.7 years) selected from a national epidemiological survey of calcaneal QUS in Taiwan. Age was multiplied by -0.2 and body weight by 0.2. Both values were truncated to yield integers, which were then added together, and compared to the QUS results.

RESULTS

When the risk category was defined as OSTA index < or = -1, and low QUS value as t-score < or = -2.5, the sensitivity and the specificity of the index were 84.0% and 61.0%, respectively, and the area under the curve was 0.81. According to the OSTA research group's classification, the high-risk subgroup (index < -4) represented 10.7% of the women 40 years or older, the intermediate-risk subgroup (index -1 to -4) 35.0%, and the low-risk subgroup (index > -1) 54.3%. The prevalence of low QUS values was high among the high-risk category (48.5%), and significantly trended downwards among the moderate- and low-risk categories (21.1% vs 4.4%). As the age of the population increased, there was an increasing false-negative rate (p < 0.001) when using OSTA > -1 to predict the normal QUS value.

CONCLUSIONS

The OSTA index, a simple and free risk assessment tool, can be used to estimate the prevalence of low QUS values in Asian women and may help to increase awareness and prevention of low bone mineral density.