Meta-Analysis: Accuracy of Quantitative Ultrasound for Identifying Patients with Osteoporosis

BACKGROUND: There is increased interest in quantitative ultrasound for osteoporosis screening because it predicts fracture risk, is portable, and is relatively inexpensive. However, there is no consensus regarding its accuracy for identifying patients with osteoporosis. PURPOSE: To determine the sensitivity and specificity of calcaneal quantitative ultrasound for identifying patients who meet the World Health Organization's diagnostic criteria for osteoporosis. Dual-energy x-ray absorptiometry (DXA) was used as the reference standard. DATA SOURCES: MEDLINE (1966 to October 2005), EMBASE (1993 to May 2004), Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Reviews (1952 to March 2004), and the Science Citation Index (1945 to April 2004). STUDY SELECTION: English-language articles that evaluated the sensitivity and specificity of calcaneal quantitative ultrasound for identifying adults with DXA T-scores of -2.5 or less at the hip or spine. DATA EXTRACTION: Two authors independently reviewed articles and abstracted data. DATA SYNTHESIS: The authors identified 1908 potentially relevant articles, of which 25 met the inclusion criteria, and calculated the sensitivity and specificity of quantitative ultrasound over a range of thresholds. For the quantitative ultrasound index parameter T-score cutoff threshold of -1, sensitivity was 79% (95% CI, 69% to 86%) and specificity was 58% (CI, 44% to 70%) for identifying individuals with DXA T-scores of -2.5 or less at the hip or spine. For a T-score threshold of 0, sensitivity improved to 93% (CI, 87% to 97%) but specificity decreased to 24% (CI, 10% to 47%). At a pretest probability of 22% (for example, a 65-year-old white woman at average risk), the post-test probability of DXA-determined osteoporosis was 34% (CI, 26% to 41%) after a positive result and 10% (CI, 5% to 12%) after a negative result when using a T-score cutoff threshold of -1. Analysis of other quantitative ultrasound parameters (for example, broadband ultrasound attenuation) revealed similar estimates of accuracy. LIMITATIONS: The relatively small number of included studies limited the authors' ability to evaluate the effects of heterogeneous study characteristics on the diagnostic accuracy of quantitative ultrasound. CONCLUSIONS: The currently available literature suggests that results of calcaneal quantitative ultrasound at commonly used cutoff thresholds do not definitively exclude or confirm DXA-determined osteoporosis. Additional research is needed before use of this test can be recommended in evidence-based screening programs for osteoporosis.