Changing order of mammogram readings not linked to improved cancer detection rate

1. Detection rate, recall rate, and rate of disagreement between readers was not affected by changing the reading order of mammograms.

2. The number of patients called back for further testing decreased as more mammograms were read in each batch.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Interpreting mammograms is a notoriously repetitive and tedious process. Cancers are often hidden within background tissue and can be difficult to detect, even for a trained eye. The difficulties in reading mammograms leads to high rates of both false-positive and false-negative results. Previous studies on similarly tedious tasks have demonstrated a phenomenon known as the “vigilance decrement.” Simply stated, the “vigilance decrement” suggests that the longer it takes to perform a monotonous but essential task, the less accurately that task is performed. Though widely applicable, this phenomenon had not been explicitly studied in breast cancer screening. Therefore the authors of this study examined whether changing the order in which batches of mammograms were read would change the cancer detection rate.

The results of this study indicated that the order in which cases were read did not significantly affect the cancer detection rate. However, the call-back rate decreased with increased reading time in batches larger than 40 cases. While strengthened by its multicenter, double-blind, randomized clinical trial design, the study was limited by a wide variability in the setting and manner in which each reader analyzed their cases. Additionally, second readers were not always blinded to the findings of the first reader, potentially leading to bias. Overall, this study highlights the limits of individual radiologists and adds an understanding of the human effects on the quality of mammograms.

Click to read the study in JAMA

Relevant Reading: Changing case order to optimise patterns of performance in mammography screening (co-ops): study protocol for a randomized controlled trial

In-Depth [randomized control trial]: This study examined a total of 1 194 147 screening mammograms from women with an average age of 59.3 years. The intervention in this study consisted of 2 radiologists reading batches of mammograms in opposite orders, whereas the control group consisted of 2 radiologists reading mammograms in the same order. Overall, the cancer detection rate was 0.88% (5272 cancers among 596 642 mammograms) in the intervention group and 0.87% (5212 cancers among 597 505 mammograms) in the control group (difference 0.01% points; 95%CI -0.02% to 0.04%). In batches that were read first each day the cancer detection rate was 0.83% (95%CI 0.76% to 0.89%) in the intervention group and 0.88% (95%CI 0.81% to 0.95%) in the control group (difference −0.05% points; 95%CI −0.15% to 0.04% points). Among batches read later in the day, the cancer detection rate was 0.85% (95%CI 0.82% to 0.89%) in the intervention group and 0.85% (95%CI 0.82% to 0.88%) in the control group (difference 0.002% points; 95%CI −0.045% to 0.050% points). Post hoc analysis revealed the odds of call-back decreased over the course of examining 40 cases (OR 0.83; 95%CI, 0.81 to 0.85).

Image: PD

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