Sydney Breast Imaging Accuracy Study: comparative sensitivity and specificity of mammography and sonography in young women with symptoms.

OBJECTIVE. We examined the age-specific sensitivity and specificity of mammography and sonography in symptomatic women to determine the age below which sonography may be the more accurate imaging test, which may guide the choice of initial breast imaging examination based on the woman's age. MATERIALS AND METHODS. Four hundred eighty subjects were sampled from all women consecutively attending a symptomatic breast clinic between 1994 and 1996 and ranging in age from 25 to 55 years. We included all 240 women shown to have breast cancer (thus avoiding selection bias) and 240 age-matched women shown not to have cancer. Mammograms and sonograms were prospectively interpreted independently and without knowledge of age by two radiologists in a blinded manner, with a third radiologist arbitrating disagreements. Sensitivity and specificity of each imaging test in relation to age were examined using logistic regression modeling, and accuracy was compared using the chi-square test for paired proportions. RESULTS. Sensitivity and specificity of each test were not linearly associated with age; however, the sensitivity of mammography increased substantially in women older than 50 years. Sonographic sensitivity of 81.7% was not significantly greater than mammographic sensitivity of 75.8% (chi(1)(2) = 2.06, p = 0.15). However, in women 45 years old or younger, the sensitivity of sonography was 13.2% (95% confidence interval, 2.1-24.3%) greater than that of mammography. The specificity of both tests was approximately 88.0%. CONCLUSION. These data show that sonography is the more accurate imaging test in women 45 years old or younger who present with breast symptoms and may be an appropriate initial imaging examination.