Fig. 3

Bland-Altman plots representing inter- and intrasite reproducibility. Bland-Altman plots show the differences of the measured 40^−∆∆Cq values per sample, site, and marker (y-axis) against the respective mean over all measurements (sites and days) (x-axis). The 24 samples are represented by either 4 or 3 measurements for the centrally extracted (study arm 1) or self-extracted (study arm 2) RNA samples, respectively. The average deviation of measurements at the respective site is indicated by the dashed horizontal line. The continuous vertical line indicates the marker-specific cutoff. ERBB2 (HER2) Human epidermal growth factor receptor 2, ESR1 (ER) Estrogen receptor, MKI67 Marker of proliferation Ki67, PGR (PgR) Progesterone receptor. a-j correspond to the ten study sites