Objective: To compare self-referred screenees with respondents to invitation for main performance indicators of mammography screening.
Setting: First round of an organised, population-based screening programme in six districts of northern Italy.
Methods: The screening test was a two-view mammography. Eligible women aged 50-69 years were invited. Self-referred attendees were accepted if they were eligible for screening and had not yet been invited or had been invited >6 months before presentation. Age-specific performance indicators were compared with the calculation of their ratio and 95% confidence intervals (CIs). Total ratios were age standardised. In situ carcinomas were excluded.
Results: The eligible population was 183 542 women. There were 112 188 respondents to invitation and 20 280 self-referred attendees. Self-referral rate was inversely related to age. Performance indicators were as follows: recall rate, 5.6% for self-referred attendees vs 5.5% for respondents (ratio 1.02, 95% CI 0.96 to 1.08); total aspiration cytology rate, 37.3% vs 28.3% (1.37, 1.24 to 1.51); biopsy rate, 17.0 vs 12.6 x 1000 (1.51, 1.35 to 1.67); total detection rate, 10.7 vs 7.5 x 1000 (1.70, 1.48 to 1.94); detection rate of pT1 carcinoma, 7.0 vs 6.1 x 1000 (1.35, 1.14 to 1.59); detection rate of pT2-4 carcinoma, 3.5 vs 1.2 x 1000 (3.51, 2.75 to 4.43); false-positive rate, 4.5% vs 4.7% (0.93, 0.87 to 0.99); positive predictive value (PPV) of mammography, 19.1% vs 13.5% (1.59, 1.39 to 1.82); PPV of biopsy, 63.7% vs 60.6% (1.13, 0.98 to 1.29); detected:expected ratio, 5.02 vs 3.37 (1.49, 1.28 to 1.74). All differences were more pronounced among or restricted to women aged 50-54 years.
Conclusions: Self-referred screenees were similar to respondents to invitation in main indicators of screening feasibility such as recall rate and PPV of biopsy, while showing important increases in detection rates and detected:expected ratios, especially among women aged 50-54 years.