Objective To analyze the association between radiologists’ performance and image position within a batch in screen reading of mammograms in Norway. Method We described true and false positives and true and false negatives by groups of image positions and batch sizes for 2,937,312 screen readings performed from 2012 to 2018. Mixed-effects models were used to obtain adjusted proportions of true and false positive, true and false negative, sensitivity, and specificity for different image positions. We adjusted for time of day and weekday and included the individual variation between the radiologists as random effects. Time spent reading was included in an additional model to explore a possible mediation effect. Result True and false positives were negatively associated with image position within the batch, while the rates of true and false negatives were positively associated. In the adjusted analyses, the rate of true positives was 4.0 per 1000 (95% CI: 3.8–4.2) readings for image position 10 and 3.9 (95% CI: 3.7–4.1) for image position 60. The rate of true negatives was 94.4% (95% CI: 94.0–94.8) for image position 10 and 94.8% (95% CI: 94.4–95.2) for image position 60. Per 1000 readings, the rate of false negative was 0.60 (95% CI: 0.53–0.67) for image position 10 and 0.62 (95% CI: 0.55–0.69) for image position 60. Conclusion There was a decrease in the radiologists’ sensitivity throughout the batch, and although this effect was small, our results may be clinically relevant at a population level or when multiplying the differences with the number of screen readings for the individual radiologists. Key Points • True and false positive reading scores were negatively associated with image position within a batch. • A decreasing trend of positive scores indicated a beneficial effect of a certain number of screen readings within a batch. • False negative scores increased throughout the batch but the association was not statistically significant.

Objectives To analyse how reader performance varied by time during the day in a population-based breast cancer screening programme. Methods A total of 2,937,312 readings from 148 radiologists and 1,468,656 women were included in this study from Norway. Number and percentages of mammographic readings, positive scores, true and false positive readings, true and false negative readings, sensitivity and specificity were presented for categories of time of day and for each day of the week. Multilevel mixed effect logistic regression models with restricted cubic splines were fitted to the data, and used to predict the odds ratio of the different performance measures. Results The following distribution was found for the performance measures during the study period: true positive: 12,463 (0.4%); false positive: 128,419 (4.4%); true negative: 2,794,636 (95.1%); and false negative: 1794 (0.06%). The percentage of positive readings (true positive and false positive) was highest before lunch and in the early afternoon (4.9%): false positive was highest in both periods (4.5%) and true positive was highest in the early afternoon (0.5%). The percentage of true negative was highest in the evening (95.6%), and of false negative was highest at lunchtime (0.07%). This corresponds to a gradually decreasing predicted sensitivity throughout the day. The opposite was observed for specificity. Conclusions Screen-reading early versus late during the day resulted in higher sensitivity, although at the cost of specificity. Despite small differences in the performance measures during the day, the results may be important in the discussion of optimal management of screening programmes.

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