REPRODUCIBILITY AND DIAGNOSTIC SENSITIVITY OF ULTRASONOMETRY OF THE PHALANGES TO ASSESS OSTEOPOROSIS

Objective: The present study was designed to assess the reproducibilit y and the diagnostic sensitivity of the amplitude-dependent speed of s ound (SoS) at the distal metaphysis of the proximal phalanges. Method: Fourteen presumably healthy volunteers were repeatedly measured every 6 weeks for approximately 6 months in order to assess the reproducibi lity of the SoS of the phalanges. We recruited 91 post-menopausal wome n, aged 55-75 years, who were divided in three groups according to the ir lumbar bone mineral density (BMD) and the existence of prevalent ve rtebral fractures. The objective was to evaluate the diagnostic sensit ivity of SoS measurements. We used DBM Sonic 1200 equipment, and asses sed the velocity at which US cross the phalanx in a lateral-medial dir ection. In post-menopausal women, BMD was measured by dual energy X-ra y absorptiometry (DXA) at the level of the lumbar spine, the total zon e of the non-dominant hip and the femoral neck zone of the non-dominan t hip. Results: The precision of the SoS measurements was 0.71 +/- 0.0 5% (mean +/- S.E.M) whereas the reproducibility was 0.95 +/- 0.06%. Su bjects with low BMD or prevalent fractures had significantly lower val ues of SoS (P < 0.001) than the controls. ROC curve analysis applied t o the study population confirmed that SoS was able to discriminate bet ween the controls and osteoporotic subjects (area under the ROC curves were 0.82 (low bone mineral density) and 0.85 (prevalent fractures), respectively). Hip BMD was found to be the most significant variable w hen comparing the controls and the low density patients by stepwise di scrimination and SoS significantly improved the discrimination between the groups when added to the hip BMD. The hip BMD was again the most discriminant variable when applying the same techniques to controls an d patients with prevalent fractures, followed by SoS and lumbar BMD. A cut-off value of 1881 m/s is defined for SoS by logistic discriminati on and likelihood ratio function. With this value, the sensitivity and the specificity for SoS used in the diagnosis of established osteopor osis were, 81.5% and 79.3%, respectively. Sensitivity and specificity were significantly improved when combining ultrasonometry and densitom etry. Conclusion: Measurement of ultrasound velocity at the phalanges appears to be a precise and reproducible technique. SoS discriminates between normal post-menopausal women and patients with either low lumb ar BMD or prevalent fractures to the same extent as BMD measurements. (C) 1998 International Federation of Gynecology and Obstetrics.