In the U.K., two film readers evaluate mammograms for signs of cancer independent of one another. According to a recent study published by JAMA, changing the order in which the two readers examine a batch of mammograms did not result in reduced breast cancer detection rates.

Sian Taylor-Phillips, PhD, of the University of Warwick in Coventry, U.K., and colleagues developed the study, which involved more than 1 million patients and took place at 46 specialized breast screening centers in England from December 2012 to November 2014. Patients were separated into more than 37,000 batches, with approximately half being interpreted by an intervention group (which changed the order for the second film reader) and the other half being interpreted by a control group.

Overall, Taylor-Phillips and colleagues found that the change did not have much of an impact at all. The intervention group’s cancer detection rate was 0.88 percent, and the control group’s cancer detection rate was 0.87 percent.

“The intervention did not influence cancer detection rate, recall rate, or rate of disagreement between readers,” the authors wrote. “There was no pattern of decreasing cancer detection rate with time on task as predicted by previous research on vigilance decrements as a psychological phenomenon. Instead there was a gradual decrease in recall rate, with an increase in [positive predictive value] and a decrease in false-positive recall of women with time on task. This may reinforce and explain previous observational research that identifies that recall rate is reduced when grouping women’s cases into batches.”

The “vigilance decrements” Taylor-Phillips et al. referenced are trends that have been observed in the past when studying other visual tasks similar to reading mammography (“decreasing detection rates with time on task,” as the authors described it.) This study did not indicate that such a phenomenon is taking place at breast screening centers.

“The vigilance decrement phenomenon has been reported in many peer reviewed publications, but was not observed in this large randomized clinical trial,” the authors wrote. “These previous studies were primarily undertaken in psychology laboratories rather than in real-life settings.”

The authors noted that their study did have limitations. Reading room conditions were not controlled, for example. In addition, statistics such as the length of the readers’ work weeks and the number of breaks they took were not tracked.