**2.1.2** *Steady-state***, biological and analytical variation**

The variations during the stable period of monitoring breast cancer patients are considered as *steady-state* and expressed as within-subject biological variation (CVB) and analytical variation (CVA) according to Sölétormos et al*.* (2000a). However, the within-subject biological variation, CVB, is not homogeneous. Therefore CVB for 5th, 50th and 95th percentile has been used with the analytical variation CVA as a constant.

For TPA the 50th percentile for within-subject biological variation, CVB%, is 24.5% and analytical variation, CVA%, is 8.4%.

For TPA the 95th percentile of within-subject biological variation, CVB%, is 48.9% and analytical variation, CVA%, is 8.4%

For TPA the 5th percentile of within-subject biological variation, CVB%, is 8.5% and analytical variation, CVA%, is 8.4% (Söletormos et al., 2000a).
