**2.2.2 Algorithm {2} Tondini & Hayes**

304 Biomarker

Barak

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**Algorithm:**

**Sample 6**

**Algorithm:**

**Sample 4**

**Algorithm:**

**Sample 2**

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0 50 100 **Start concentration**

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Fig. 4. Percentages positive signals at three different times.

Percentage positive (POS) as a function of starting concentration (TPA U/L) for algorithm {1} Barak et al. after 2 months (sample 2), 6 months (sample 4) and 10 months (sample 6). Same slope symbols as in

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**Percentage positive**

Fig. 2.

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**Percentage positive**

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Two consecutive measurements. The last measurement is above the cut-off and at least 25% higher than any previous concentration below the cut-off value (Tondin & Hayes, 1989).

The only difference between algorithm Barak et al. {1} and algorithm Tondini & Hayes {2} is that, in the latter algorithm, the criterion is 25% higher concentration above cut-off compared to the lowest value below cut-off. Many (simulated) patients will be recorded similarly as algorithm Barak et al. {1} - especially with low start concentration. Therefore, the performances of these two algorithms are comparable. Algorithm Tondini & Hayes {2} shows only moderately lower percentages of positives (POS) for the lower tumour growths and the steady-state situation at 6 months, i.e. also slightly lower FP between 55 and 95 U/L during the first half of the year (compare Fig. 4 and Fig. 5 at sample 4).

Although there are a few more restrictions in algorithm Tondini & Hayes {2}, the detection time for TP patients is practically the same – however, the percentage of FP is still unacceptable with start concentrations near cut-off.
