**2.2.5 Algorithm {5} Sölétormos et al. B**

At least three measurements. The last measured concentration is higher than the penultimate concentration, both above the cut-off, and higher than the third to last measured concentration. The penultimate concentration is significantly higher than any previous measurements below the cut-off (Söletormos et al., 1996).

In a comparison of algorithm Chan et al. {4} with algorithm Söletormos et al. B {5}, the latter algorithm is much more restrictive in recording positive signals (POS). The last measurement demands an increase compared to the penultimate value – and this

Computer Simulation Model System for Interpretation

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**Percentage positive**

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and Validation of Algorithms for Monitoring of Cancer Patients by Use of Serial Serum... 309

Nicolini

Nicolini

Nicolini

**Algorithm:**

**Sample 13**

**Algorithm:**

**Sample 10**

**Algorithm:**

**Sample 7**

0 50 100 **Start concentration**

0 50 100 **Start concentration**

0 50 100 **Start concentration**

months) the figures will "freeze" and be identical for the three tumour slopes. Fig. 6*.* Results from Algorithm {7} Nicolini et al. at different times

Percentage positive (POS) as a function of starting concentration for algorithm {7} Nicolini et al. after 1 year (sample 7), after 18 months (sample 10), and after two years (sample 13). After sample 8 (14

penultimate value has to have a significant increase compared to earlier measurements (see below). The more restrictive criteria are shown to give much lower FP signals – even after two years, the percentages of FP results are 24% compared to 91% at algorithm Chan et al. {4} below 95 U/L. Again more restrictive criteria have a 'cost' in regard to detection time here at the slowest slope, which is extended by two months at algorithm Söletormos et al. B {5}. On the other hand these algorithms show only 0% FP results at low start concentrations, i.e. below 57 U/L.

The significant increase, or reference change value (RCV), was introduced by Harris and Yasaka (1983) in order to detect a significant change in consecutive measurements, and was defined as RCV = 1.96\*2½\*CVB, where the 1.96 is the standard deviation from a Gaussian distribution corresponding to a two-tailed probability of 5 %, and 2½ relates to the variation of differences CVDifference = (CVB2 + CVB2)½ or the CVB2 can be substituted by the combination of biological and analytical variation. The calculation in the computer system is the test of the difference between two consecutive measurements (as a percentage) in regard to the RCV.
