Observer Variability in Breast Cancer Diagnosis between Countries with and without Breast Screening

Image reporting is a vital component of patient management depending on individual radiologists' performance. Our objective was to explore mammographic diagnostic efficacy in a country where breast cancer screening does not exist.

Two mammographic test sets were used: a typical screening (TS) and high-difficulty (HD) test set. Nonscreening (NS) radiologists (n = 11) read both test sets, while 52 and 49 screening radiologists read the TS and HD test sets, respectively. The screening radiologists were classified into two groups: a less experienced (LE) group with ≤5 years' experience and a more experienced (ME) group with ≥5 years' experience. A Kruskal-Wallis and Tukey-Kramer post hoc test were used to compare reading performance among reader groups, and the Wilcoxon matched pairs tests was used to compare TS and ND test sets for the NS radiologists.

Across the three reader groups, there were significant differences in case sensitivity (χ² [2] = 9.4, P = .008), specificity (χ² [2] = 10.3, P = .006), location sensitivity (χ² [2] = 19.8, P < .001), receiver operating characteristics, area under the curve (χ² [2] = 19.7, P < .001) and jack-knife free-response receiver operating characteristics (JAFROCs) (χ² [2] = 18.1, P < .001). NS performance for all measured scores was significantly lower than those for the ME readers (P < .006), while only location sensitivity was lower (χ² [2] = 17.5, P = .026) for the NS compared to the LE group. No other significant differences were observed.

Large variations in mammographic performance exist between radiologists from screening and nonscreening countries.