Accuracy depends on number of mammograms read

Suleiman et al report in the Journal of Medical Imaging, the effect the number of screening mammograms read per year has on the performance of expert radiologists from Australia and the United States in the detection of breast cancer.

Forty-one radiologists, 21 from Australia and 20 from the United States, reviewed 30 mammographic cases.  Twenty cases were abnormal while 10 cases were normal mammograms. Radiologists were asked to locate malignancies and assign a level of confidence. A jackknife free-response receiver operating characteristic, figure of merit (JAFROC, FOM), inferred receiver operating characteristic, area under curve (ROC, AUC), specificity, sensitivity, and location sensitivity were calculated using Ziltron software and JAFROC v4.1. A Mann-Whitney U test was used to compare the performance of Australian and U.S. radiologists.

The results showed that when radiologists’ experience and number of mammograms were reading per year were taken into account, the Australian radiologists sampled showed significantly higher sensitivity and location sensitivity while JAFROC (FOM) and inferred ROC (AUC) analyses showed no difference between the overall performance in the two countries. Receiver operating characteristic and location sensitivity were higher for the Australian radiologists who read the most cases per year.