Evaluation of osteoporosis using skin thickness measurements

Measurement of skin thickness has been proposed as a method of predicting low bone mineral density (BMD) and the consequent risk of osteoporotic fracture in postmenopausal women. The Episcan I-100 device is a new type of ultrasound device that uses high-frequency (20 MHz) ultrasound to measure skin thickness using a small probe placed on the skin. The aims of this study were to investigate whether there is any correlation between skin thickness as measured by ultrasound and BMD as measured by dual-energy X-ray absorptiometry, to establish whether patients with osteoporotic fractures have reduced skin thickness, and to investigate the relationship between skin thickness and clinical risk factors for osteoporosis. Short-term precision based on duplicate measurements on 132 patients gave a coefficient of variation of 3.2%. Small but statistically significant correlations between skin thickness measurements and BMD measurements at axial and peripheral sites were observed (r = 0.21-0.29, P < 0.0001). An odds ratio of 1.42 was found for identifying patients with a prevalent fracture at any skeletal site, suggesting that skin thickness measurements can discriminate patients with fractures. ROC analyses also demonstrated the ability of skin thickness measurements to discriminate fracture patients from controls. When measured by the decrease in Z-score, clinical risk factors for low BMD were found to affect skin thickness measurements to a similar extent as spine and hip BMD measurements. Skin thickness measurements have limited utility in identifying patients with low bone mass.